Cannot connect to any Wifi network in Ubuntu 20.04

I upgraded to Ubuntu 20.04 from 19.10 and my wifi adapter is not connecting to any Wifi network. It scans all available networks but is unable to connect to any network.I tried all possible solutions found in the internet but no use. Please help!  Following are the details of my wireless card:DMI   *-network                       description: Ethernet interface        product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller        vendor: Realtek Semiconductor Co., Ltd.        physical id: 0        bus info: pci@0000:02:00.0        logical name: enp2s0        version: 15        serial: 04:d4:c4:e2:da:b4        capacity: 1Gbit/s        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress msix bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation        configuration: autonegotiation=on broadcast=yes driver=r8169 firmware=rtl8168h-2_0.0.2 02/26/15 latency=0 link=no multicast=yes port=MII        resources: irq:49 ioport:e000(size=256) memory:f7804000-f7804fff memory:f7800000-f7803fff   *-network        description: Wireless interface        product: RTL8822CE 802.11ac PCIe Wireless Network Adapter        vendor: Realtek Semiconductor Co., Ltd.        physical id: 0        bus info: pci@0000:04:00.0        logical name: wlp4s0        version: 00        serial: 80:91:33:c9:2b:d5        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless        configuration: broadcast=yes driver=rtw_8822ce driverversion=5.4.0-29-generic firmware=N/A latency=0 link=no multicast=yes wireless=IEEE 802.11        resources: irq:62 ioport:d000(size=256) memory:f7600000-f760ffff   *-network        description: Ethernet interface        physical id: 1        bus info: usb@1:3        logical name: enxfcde56ff0106        serial: fc:de:56:ff:01:06        capabilities: ethernet physical        configuration: broadcast=yes driver=rndis_host driverversion=22-Aug-2005 firmware=RNDIS device ip=192.168.1.101 link=yes multicast=yes


How to prove $ \mathrm{e}^x\left|\int_x^{x+1}\sin\mathrm e^t \,\mathrm d t\right|\leqslant 2$?

I want to prove $$ \mathrm{e}^x\left|\int_x^{x+1}\sin\mathrm e^t \,\mathrm d t\right|\leqslant 2. $$ I tried to use Cauchy–Schwarz inequality and some other basic integral inequalities but failed.   Any suggestions will be appreciated.


Why would a partition be in use by the system if it isn't mounted?

I've been migrating my system from btrfs to ext4 after running into performance issues with VMs. I have two hard drives in my laptop to work with. I've successfully moved my home partition, but the same steps I used aren't working for root.  Progress so far:  I've dd'd my root partition from /dev/sda3 into /dev/sdb3. I modified /etc/fstab to the following:  $ cat /etc/fstab #  # /etc/fstab: static file system information # # <file system> <dir>   <type>  <options>       <dump>  <pass> # UUID=95f13c34-96ca-49e3-bcb2-ff594df31506 /dev/sdb3               /               btrfs           rw,noatime,ssd,space_cache,discard      0 0  # UUID=0fe04f59-599f-41e2-ac30-2ad0f17a9727 /dev/sda2               /boot           ext2            rw,relatime     0 2  # UUID=44741e0f-924a-4841-80ef-2132bef84182 /dev/sda4               /home           ext4            rw,noatime,discard      0 0   and run sudo mkinitcpio -p linux. It seems to work. I'm able to boot by mounting the partition on the second disk. df shows:  $ df Filesystem      Size  Used Avail Use% Mounted on /dev/sdb3        28G   18G  9.8G  65% /   So, clearly, sdb3 is mounted, not sda3. Here's the problematic step: When I try to format sda3, which is supposedly unused, I get the following:  $ sudo mkfs.ext4 /dev/sda3 [sudo] password for stew:  mke2fs 1.42.11 (09-Jul-2014) /dev/sda3 contains a btrfs file system Proceed anyway? (y,n) y /dev/sda3 is apparently in use by the system; will not make a filesystem here!   sda3 is in use. How and why could it possibly be in use?  As per casey's comment, the output of mount:  mount | grep sd /dev/sdb3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime)   As per Warwick's comment, unmounting:  $ sudo umount /dev/sda3 umount: /dev/sda3: not mounted   Mounting and umounting sda3 elsewhere works successfully, but changes nothing.  Update: More fishy behavior:  $ mount | grep sd /dev/sdb3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime) $ sudo mount /dev/sda3 mnt [sudo] password for stew:  $ mount | grep sd /dev/sda3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime) /dev/sda3 on /home/stew/mnt type btrfs (rw,relatime,ssd,discard,space_cache)   After mounting sda3, sdb3 is no longer mounter. Weird, huh?  As per mikeserv:  $ rmmod btrfs rmmod: ERROR: Module btrfs is in use   This is very much expected, since sdb3 is btrfs and supposed to be mounted to root. From my mkinitcpio.conf file:  MODULES="" HOOKS="base udev autodetect modconf block filesystems keyboard fsck"


What is the concept (or idea) behind "induced subgraph" definition?

Let $G, G'$ be graphs.  If $G' \subseteq G$ and $G'$ contains all the edges $xy \in E$ with $x,y \in V'$, then $G'$ is an induced subgraph of $G$. We say that $V'$ induces or spans $G'$ in $G$, and write $G'=:G[V']$. Thus if $U \subseteq V$ is any set of vertices, then $G[U]$ denotes the graph on $U$ whose edges are precisely the edges of $G$ with both ends in $U$.   Can I say that the term "induced" brings some sort of equivalence meaning? So that, if some equivalence holds, I can use smaller structures for my convenience.  In other words, does the graph $G'$ preserve some sort of structure or properties belonging to graph $G$?


What should I read to understand the math behind waves?

I'm learning differential equations and waves - following online courses and reading some textbooks - and I find that quite often, the use of Phasors, equations combining sinusoidal waves of different amplitudes and frequencies (the derivation of beats)...etc...they're explained really briefly, without a lot of diving deeper into them, and then applied. Is there a specific "math" which I could study, or textbook I could read, that presents these subjects more explicitly? The more geometric and intuitive the math book is, the better! I tried looking for "wave mathematics" but...found mostly really advanced books. Complex Analysis didn't seem to fit either. All and any recommendations are welcome.  Edit: Books on the differential equations of waves are helpful...but, that's not really what I meant. What I really want is something that starts simpler. What led me to asking this question is that it took me a long time to understand the geometric intuition for how to combine waves of the same amplitude but different frequencies (for which this -  - helped quite a bit) and I still don't understand at all how to combine them if they have different amplitudes! Is there not anything simpler than a differential equations approach, or perhaps a book that DOES go into the differential equations, but also does so explaining each step, instead of skipping over the "basic" math of waves? Thanks again.


Show that if p is prime then p not= (a/b)^2 for a and b integers.

Can anyone help with this Abstract Algebra problem? Thank you so much! Show that if p is prime then p not=(a/b)^2 for a and b integers.


If I draw something with a brush then use Live Paint, how do I get rid of the brush stokes?

Say I have the following picture that I drew with a black brush then used Live Paint to color it.   How do I get rid of the black stroke?


Why do the two slits of a double slit experiment not make light coherent and create an interference pattern if monochromatic light is passed through?

If a narrow slit makes monochromatic light coherent, why is light required to pass through the single slit before the double slits in Young's experiment? Wouldn't the double slits individually make light coherent if narrow enough and then form an interference pattern without a single slit?


How do I increase the spacing between the subsection number and header name in the table of contents. I am using www.sharelatex.com.   When I have a large number of subsections the section numbers and headers overlap.   \documentclass[12pt, openany]{book}  % geometry sets paper dimensions \usepackage[    paperheight=8in,                 paperwidth=6in,                 top=.1in,                 bottom=.2in,                 right=.1in,                 left=.1in,                 heightrounded]{geometry}   % Font Style \usepackage{bookman}  \begin{document}  \tableofcontents \setcounter{tocdepth}{3}  \chapter{Test} \chapter{Test} \chapter{Test} \chapter{Test} \chapter{Test} \chapter{Test} \chapter{Test} \chapter{Test} \chapter{Test} \chapter{Test} \section{Test} \subsection{Test} \subsection{Test} \subsection{Test} \subsection{Test} \subsection{Test} \subsection{Test} \subsection{Test} \subsection{Test} \subsection{Test} \subsection{Test} \subsection{Test}  \end{document}   Edit: 12-22-2014 Found an answer to my question at   I added these two lines to the preamble.  \usepackage[tocindentauto]{tocstyle} \usetocstyle{KOMAlike}


Find all $n$ such that i. $\phi(n)=\frac n2$, ii. $\phi(n)=4$.

For $n\ge1$, let $\phi(n)$ be the number of positive integers $\le n$, which are relatively prime to $n$  i. Find all $n$ such that $\phi(n)=\frac n2$ ii. Find all $n$ such that $\phi(n)=4$.  I know the formula for suker totient function but that is not telling me anything. Please help.


Can I use B1/B2 visa to travel to the US without a business purpose?

I got a B1/B2 visa earlier this year when I traveled to the US for a business trip from my company. It expires in 2013 and I'd love to visit the United States again, but for no other purpose than traveling.  I wonder:        If I can legally travel to US with B1/B2 visa without a real business need (assuming I'm honest);   If I have to work at my current company to be able to use it.      I live in Russia.


How to straighten a bent derailleur hanger?

I've bent (again) my derailleur hanger. It's a replaceable hanger but for this summer I can't get an original one and I know that the non-original one I can get is made in a harder material and could possibly damage the frame.  So I'm left with the choice of straightening this light aluminium alloy thing. How do I do that without breaking/weakening it?


I've read the answers to this question, but still don't understand what to do:    I am logged onto my Ubuntu server as root. I have the following command in my .profile:  alias test-alias="echo test"   I have the following command in my crontab file:  11 9 * * *      source /root/.profile; test-alias > /root/tmp.output 2>&1   When this command runs, the only output present in tmp.output is:  /bin/sh: 1: test-alias: not found   What am I doing wrong here? How can I use my test-alias in my crontab file? I want to use the alias directly in the command, I don't want to create additional scripts to run the alias.


Why can't I create an array of a type parameter in Java?

Well, I have read a lot of answers to this question, but I have a more specific one. Take the following snippet of code as an example.  public class GenericArray<E>{     E[] s= new E[5]; }   After type erasure, it becomes  public class GenericArray{     Object[] s= new Object[5]; }   This snippet of code seems to work well. Why does it cause a compile-time error?  In addition, I have known from other answers that the following codes work well for the same purpose.  public class GenericArray<E>{     E[] s= (E[])new Object[5]; }   I've read some comments saying that the piece of code above is unsafe, but why is it unsafe? Could anyone provide me with a specific example where the above piece of code causes an error?  In addition, the following code is wrong as well. But why? It seems to work well after erasure, too.  public class GenericArray<E>{         E s= new E();     }


How easy is it to upgrade from 18.04 beta 1 to 18.04 final release?

I have a new ASUS Vivobook laptop and am wondering which version of Ubuntu to install given that 18.04 LTS is scheduled for release at the end of this month.  I took a look at the  and did some research on  and see it's possible to upgrade directly from 16.04 or 17.10.  However I was wondering if installing  is perhaps an even better solution - will upgrading from the beta version to the stable version at the end of April be the easiest option?  If installing the beta version of 18.04 is not recommended, which will be a least error prone upgrade to 18.04 - 16.04 or 17.10?


How to load tiles of a specific area in OpenLayers 3 using a bounding box

I have built a simple OpenLayers 3 map, see below for code:  HTML code:

   CSS:  #map{      width:100%;      height:800px; }          OpenLayers map initialization code:  var map;     function init(){     map = new ol.Map({         target:'map',         renderer:'canvas',         view: new ol.View({             projection: 'EPSG:900913',             center:[-8015003.33712,4160979.44405],             zoom:5         })     });       var newLayer = new ol.layer.Tile({     source: new ol.source.OSM()     });     map.addLayer(newLayer); }   Now my map loads just fine, what I would really like to do is, I would like to have only a specific area loaded, for which I need a bounding box, I would like to load the the bounding box for  area. But I am new to OpenLayers 3, so I tried and I just couldn't make the bounding box.  Can somebody help me make the bounding box please?


Would the Picard Maneuver work in the Star Wars universe?

The  basically boils down to: "surprise your enemy by jumping right next to him and unload all your cannons". However, Trek canon makes a bit more of a technological fuss about how it works.  Seeing that the Star Wars universe also has FTL travel, I wondered if:   the Picard Maneuver would be technically possible in SW and  if there are any references (probably by a different name) in the SW universe.


The product of $n$ consecutive integers is divisible by $n$ factorial

How can we prove that the product of $n$ consecutive integers is divisible by $n$ factorial?     Note: In this  and the comments here the OP has clarified that he seeks a proof that "does not use the properties of binomial coefficients". Please post answers in said newer thread so that this incorrectly-posed question may be closed as a duplicate.


Let $K \subset [0,1]$ be the Cantor set. show that $f : [0, 1] \to \mathbb R$...

Let $K \subset [0,1]$ be the Cantor set. show that $f : [0, 1] \to \mathbb R$ given by $$f(x) = \begin{cases} 1, & x \in K \\                        0, & x \in [0, 1]\setminus C \end{cases}$$ is integrable and calculate $\int_0^1 f(x)dx$.  My attempt: The Cantor set $K$, although not countable, has a null measure. Thus, if we stop $n$-th step of its construction, we will see that the Cantor set is contained in the collection of $2^n$ intervals, each having length $\frac{1}{3^n}$.Given $ \epsilon \gt 0$, we can take $n \in \mathbb N$ such that $\frac{2}{3^n} \lt \epsilon$ and we conclude that the measure of $K$ is zero. Now, as [ 0.1] is closed then $[0,1] - K$ is open, the function $f$ is locally constant, and therefore continues, at points $x \notin K$. Since $K$ has no interior points, $f$ is discontinued at all $K$ points. By the theorem(If every set D of the discontinuity points of a bounded function $f:[a,b] \to \mathbb R$ has null measure then $f$ is integrable) $f$ is integrable. Given any partition $P$ of [0,1] all ranges of $P$ contain points that do not belong to $K$, since int $K = \emptyset$. Thus, $m_i=0$ and $s(f;p)=0$ for every partition $P$. It then follows that $\int_0^1 f(x)dx = \underline\int_0^1f(x)dx = 0$. Thank's in advance for any help.


Marketing Cloud SQL using CHARINDEX and LEFT / RIGHT

im trying to grab the value of a text field in a Data extension. It has a specifix syntax: example_IWantToGrabThis_example I want to grab the value between the underscores. I think i need to use CHARINDEX  with Left and right but cannot seem to find examples that work in Marketing Cloud. Kind regards Rob


Java Regex matching url with/without http or with/without www

could you please someone tell me how to match these types of url in string?  For example:  example.com www.example.com http://example.com https://www.example.com example.com/exam1/exam.php example.com/exam ...   Actually, I need to detect all forms of URL you can see for example on Twitter in plain text.  I have tried to find some regex by google but I couldn't find something which fits all the types in Java.  UPDATE: Maybe I wasn't too precise - I need find all these types of url in plain text and replace them by some token. For example: status.replaceAll(yourRegex, "URL");  Thank you!


What is the "?" symbol in URL used for in php?

I am new to PHP. In the path of learning PHP language, I notice that, some website would this kind of URL:  www.website.com/profile.php?user=roa3&...  My questions:   What is the "?" symbol used for?  If I were develop a php website, must I use it in my URL? For example, after a user(roa3) successful logged in, I will redirect to "www.website.com/profile.php?user=roa3" instead of "www.website.com/profile.php" What are the advantages and disadvantages of using it?


How to resize Ubuntu & Windows partitions?

I've set my grandson's laptop to be able to dual boot (Vista and Ubuntu). I'd like to give as much space as possible to Ubuntu as Windows isn't used much. I'm  pretty noob to Linux and have no real idea how to use gparted.  Here is a screenshot of gparted; it'd be great if someone could explain what it means and how to give more space to Ubuntu and less to Windows.


Hierarchical clustering with categorical variables - what distance/similarity to use in R?

I have only categorical variables in my database.  What distance/similarity to use?  I´m using the function simil() (library(proxy) in R.


Should Likert scale measures be treated as interval, ratio, ordinal, or nominal?

Forgive me, I am forgetting my basic statistics.


Find a set of colors based off of another set

new here first off, so if I need to redirect please let me know kindly.  I am a developer and am currently working on front end stuff, and I need to come up with a set of colors for something I am doing based off of another existing set. The colors I have are:   color: #8a6d3b; //darker brown yellow background-color: #fcf8e3; //eggshell yellow border-color: #faebcc; //slightly darker from above^   There exists 4 of these sets of colors, and I want to make my own for use with my web application. I assume though cannot verify that they use some kind of scale to determine these colors. Say they know what they want the background-color to be, and then decide they want the color to be 50 values below that and the border-color to be only 20 values darker than the background. Are there any tools or methods to determine how much variance in the colors there is so if I give a background color, I could then determine the other colors based on the variance?  I'm not versed in the graphic design world/terminology, so hopefully you get the idea of what I am trying to say. Thanks!


Use Case:  What i want is a list of records, and allow this user to choose 2 of those records, then click a button to go to a new VF page, if the user selects more than 2, i want him to get a notification of some kind saying you need to select 2 records, I do not want the page refeshed though.  Strategy:  I'm creating a wrapper class for the records like this:  and i have that part going by creating a custonm controller... I need the notification part working.   Problem:  I don't know how to call methods from the customController in javascript Also, i do not want to refresh the entire page. I just want them to go back to where they were. I was thinking a pop-up notification but I'm flexible..


What is the term for a pet name used in a sense of derision?

I found out today that the term for pet names used in an affectionate or an endearing way is hypocorism, I searched online but I couldn't find a term for nicknames used in a derisive sense, such as a term for a teacher that pupils hate. In a sense it would be an antonym for hypocorism, maybe I'm overlooking something obvious.  Looking at the etymology, hypocorism comes the Greek verb for speaking in a childish manner, which itself is a compound of 'underneath' and 'to caress'. It doesn't appear to provide an easy antonym.


Merge two lists with specific element placement, python

Say I have two lists with strings:  list_a=["a", "c", "e"]  list_b=["b", "d", "f"]   I tried  combined = zip(list_a, list_b)   which forms a vertical list, but then I could only print it in the form of  [(a, b,), (c, d), (e, f)]   How could I achieve a list in the form of:  combined = ["a",  "b", "c", "d", "e", "f"]


When we talk about software, should we use "on" or "in"? For example:   How can I import pictures in/on photoshop? I installed new software in/on my windows. How can export files in/on adobe premiere pro?


Blank screen after I press try Ubuntu without installing

I am trying to install Ubuntu 13.10. I get just a blank screen after I press Try Ubuntu without installing. I was thinking it would be an issue with nomodeset, but when I press F6 on the screen with Other Options, nothing happens.


I see an example for standardizing data value . For better illustration, the table is shown below  I did the same thing in excel and as you can see, the results are different.  For mean and variance, I used AVERAGE and VAR formulas, respectively in Excel. The standardized values are calculated as: 0  ->  (0-2.5)/3.5 = -0.714 ...  What is wrong then?


My /boot partition hit 100% and now I can't upgrade. Can't remove old kernels to make room

My first issue was when I tried to apt-get update or apt-get upgrade. On upgrade I get the following error:  You might want to run 'apt-get -f install' to correct these. The following packages have unmet dependencies: linux-image-server : Depends: linux-image-3.2.0-27-generic but it is not installed E: Unmet dependencies. Try using -f.   I tried running apt-get install -f and this was the output(after saying yes on prompt)  (Reading database ... 186183 files and directories currently installed.) Unpacking linux-image-3.2.0-27-generic (from .../linux-image-3.2.0-27-generic_3.2.0-27.43_amd64.deb) ... Done. dpkg: error processing /var/cache/apt/archives/linux-image-3.2.0-27-generic_3.2.0-27.43_amd64.deb (--unpack):  failed in write on buffer copy for backend dpkg-deb during `./boot/System.map-3.2.0-27-generic': No space left on device  No apport report written because the error message indicates a disk full error                                                                           dpkg-deb:    error: subprocess paste was killed by signal (Broken pipe) Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-27-generic   /boot/vmlinuz-3.2.0-27-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-27-generic /boot/vmlinuz-3.2.0-27-generic Errors were encountered while processing: /var/cache/apt/archives/linux-image-3.2.0-27-generic_3.2.0-27.43_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1)   I tried running apt-get autoremove and it gives me the same error as apt-get upgrade.  When I run df, I get this for /boot:  /dev/sda1                    233191     230297         0 100% /boot   So, I read elsewhere that I should try to purge old kernels. I checked for what kernels I had with:  $ dpkg -l linux-image-\* | grep ^ii ii  linux-image-2.6.38-13-server  2.6.38-13.52  Linux kernel image for version 2.6.38 on x86_64 ii  linux-image-3.0.0-13-server   3.0.0-13.22   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-14-server   3.0.0-14.23   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-15-server   3.0.0-15.26   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-16-server   3.0.0-16.29   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-17-server   3.0.0-17.30   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.2.0-24-generic  3.2.0-24.39   Linux kernel image for version 3.2.0  on 64 bit x86 SMP ii  linux-image-3.2.0-25-generic  3.2.0-25.40   Linux kernel image for version 3.2.0  on 64 bit x86 SMP ii  linux-image-3.2.0-26-generic  3.2.0-26.41   Linux kernel image for version 3.2.0  on 64 bit x86 SMP   When I try to remove the oldest with this:  $ sudo apt-get purge linux-image-2.6.38-13-server Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: linux-image-server : Depends: linux-image-3.2.0-27-generic but it is not going to be     installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   How can I free up or extend boot without messing up my installation?


All I remember about the book is that the protagonist was a human female fighter pilot, she has short hair, not sure if it was blond or auburn and she was involved in making peace with the alien race.  The alien race was invading Earth, but because of her they stopped, surrendered and because of her helped Earth improve its technology. I remember that she melded with something and was starting to sort of think like them and lose a bit of her humanity.  It was set in the not too distant future. I believe I read it in the 90s.


Prove that the Rationals are Countably Infinite

I was assigned to Prove that $\mathbb{Q}$ is countably infinite  I did the following:  We define $\mathbb{Q}= \lbrace \frac{a}{b} \mid a, b \in \mathbb{Z}_{>0} \rbrace$. Also define $\mathbb{Q} \xrightarrow{a} \mathbb{Z}_{>0} \times \mathbb{Z}_{>0}$ as $\forall a, b \in \mathbb{Z}_{>0}$ where $\frac{a}{b} \in \mathbb{Q}$, $q(\frac{a}{b})=(a,b)$. Then since $\mathbb{Z}_{>0}$ is countably infinite, and by the fact that the Cartesian product of two countably infinite sets is countably infinite, $\mathbb{Z}_{>0} \times \mathbb{Z}_{>0}$ is countably infinite with some mapping $\mathbb{Z}_{>0} \times \mathbb{Z}_{>0} \xrightarrow{b} \mathbb{Z}_{>0}$. Then the composite function $a \circ b$ is a bijection $\mathbb{Q} \xrightarrow{a \circ b} \mathbb{Z}_{>0}$ proving $\mathbb{Q}$ is countably infinite.   My question: is there any alternative way to prove this or is there any way to strengthen my proof or change it?


Why do some tags have image attachments?

I see some tags have images and some do not, why is this?


Comparing Two Sums with Binomial Coefficients

How do I use pascals identity:  $${2n\choose 2k}={2n-1\choose 2k}+{2n-1\choose 2k-1}$$ to prove that  $$\displaystyle\sum_{k=0}^{n}{2n\choose 2k}=\displaystyle\sum_{k=0}^{2n-1}{2n-1\choose k}$$  for every positive integer $n$ ?


I've been reading (most) questions and answers (here) about baking bread (which I love) and how to replace eggs in many recipes (which I wish I didn't need). Turns out, I too have egg allergy (not too severe) and a few of my favorite breads require one or more eggs.  So far I've seen two options, in many threads, that look promising: Ener-G egg replacer and replacing eggs with flax. However, not a single use case I've seen here is about bread. I'm looking for an option to replace 1-3 eggs in a bread dough with: 500 g of white wheat flour, 200 ml of milk, 50-80 g of butter, a variable amount of sugar (5-50 g) and 20-30 g of fresh yeast.  Examples of this dough are the , the  and a similar recipe from Galicia (northwest Spain) with even more eggs. And so many other breads, but these are my favorite ones :)  Has anyone tried flax or ener-g on a similar bread dough?


HP530 Ubuntu 12.04 Black screen after restart

I installed a fresh copy of ubuntu 12.04. I started the machine and was able to login successfully the first time. Upon any restarts I see a black screen, then I hear the audio drum roll that is played when it is time to login, I however only have a black screen. I then loaded up grub loader by holding shift during booting and set to nomodeset(I believe this goes low graphics default). I am able to boot in. I downloaded and ran boot repair, below you can find the boot report. Upon running boot repair and restarting it boots in fine the first time. However on subsequent attempts it will just go to the black screen. Please Help!


triggering an on('click') from loaded content

I have two pages: edit.php and list-questions.php. I am wanting to load content from list-questions to edit, this works.  I also want to be able to trigger on('click') from list-questions within edit.  Within Edit.php I have:

   And within list-questions.php I have:  <?php $catID = $_GET['id'];  $getItems = $con->prepare("SELECT itemID,itemName,itemType FROM items WHERE catID=?"); $getItems->bind_param("i", $catID); $getItems->execute(); $getItems->store_result(); if($getItems->num_rows > 0) { ?>

Questions

 <?php   $getItems->bind_result($itemID,$itemName,$itemType);   while($getItems->fetch()) { ?>

<?php echo $itemName; ?>
	            <a class="trg-delete confirm" data-id="<?php echo $itemID; ?>">
 <?php }; ?>
 <?php } else { ?>

Questions

No Questions Found

 <?php };   When questions are found it outputs something similar to (simplified):

Questions

Question?

   How would I go about listening for a click from .trg-delete in edit.php ?


Let I have an array [1,2,3,4,5...] and i want to show it in a UIPickerView in swift. But i would like to be it rotational. For e.g after the value 5 next value will be 1, then 2 and so on. Similarly while showing the selected value 1 the previous value will be 5 & so on. To be exact I would like to have the picker view like following  ->1-> |   2   | |   3   | |   4   | |   5   | |   6   |  <- 7<-


Will buying a digital full game from the xbox live marketplace still keep the data on the hard drive?

This is basically a question that applies for any game, but basically, what happened is that my disc for 'Payday 2' got scratched, and even after repairs, the game still cannot be read, and i am nervous about getting a disc in case the same happens again, so i hope to get it off the xbox live marketplace. My question is, will this new game keep the data that is saved to the hard drive, or will i have to get a new disc for this to work?  P.S. if so, will this be the same with other discs?


Selenium: reuse existing browser session, instead of opening new windows?

This has been asked a million times on the web, but there's no clear cut answer. I tried "-browserSessionReuse" today without any luck; my tests keep spawning new browser windows.  X:\QA\Automation\SELENIUM_SERVER>java -jar selenium-server-standalone-2.8.0.jar -log "log.txt" -browserSessionReuse -forcedBrowserMode "*googlechrome" <snip> 13:42:25.923 INFO - Will recycle browser sessions when possible.   Maybe it's how I'm starting Selenium in my .py files?  sel = selenium('localhost', 4444, "*chrome", 'http://server/') sel.start()   ...perhaps I'm doing too many server starts?


What are Covering Indexes and Covered Queries in SQL Server?

Can you explain the concepts of, and relationship between, Covering Indexes and Covered Queries in Microsoft's SQL Server?


Ubuntu 14.0.4 apt-get update fails for any installs and upgrades in trusty

I have tried various recommendations from the web to no success. The apt-get update gives errors . Here are my error messages after sudo apt-get udpate:  W: Failed to fetch http://ppa.launchpad.net/upubuntu-com/java/ubuntu/dists/trusty/main/binary-amd64/Packages  404  Not Found W: Failed to fetch http://ppa.launchpad.net/upubuntu-com/java/ubuntu/dists/trusty/main/binary-i386/Packages  404  Not Found E: Some index files failed to download. They have been ignored, or old ones used instead.   I have reviewed and tried the existing stackexchange answers that are not working for me. Trying to cleanup the ppa as per advice in sourcse gives me the following errors :  For example, the following command to remove the ppa shows other scary messages :  winsella@winsella:~$ sudo rm /etc/apt/sources.list.d/ppaname-ppa-$(lsb_release -sc).list* [sudo] password for winsella: no talloc stackframe at ../source3/param/loadparm.c:4864, leaking memory Failed to open /var/lib/samba/private/secrets.tdb tdbsam_open: Failed to open/create TDB passwd [/var/lib/samba/private/passdb.tdb] tdbsam_getsampwnam: failed to open /var/lib/samba/private/passdb.tdb! tdbsam_open: Failed to open/create TDB passwd [/var/lib/samba/private/passdb.tdb] tdbsam_getsampwnam: failed to open /var/lib/samba/private/passdb.tdb! tdbsam_open: Failed to open/create TDB passwd [/var/lib/samba/private/passdb.tdb] tdbsam_new_rid: failed to open /var/lib/samba/private/passdb.tdb! rm: cannot remove ‘/etc/apt/sources.list.d/ppaname-ppa-trusty.list*’: No such file or directory


Center the "part name" in the table of contents

I want to change in the table of contents the look of the parts. I reproduced on Word what I want :     I've looked into the site if the question was already answered but I didn't found what I want.   All I want is to center the part name in the TOC and also get rid of the page number. I am using the book class and I don't want to use other document classes.   Thank you.   EDIT. Here is my MWE :   \documentclass{book} \begin{document} \tableofcontents \part{First part} \chapter{A first chapter} \chapter{A second one} \part{Second part} \chapter{A third one} \chapter{The last one} \end{document}   Here is my preambule with titlesec :  \documentclass{book}  %Redifining paragraph spacing and thus spacing in the TOC \usepackage{titlesec} \usepackage{parskip} \setlength{\parskip}{ 0.4\baselineskip} \titlespacing\section{0pt}{9pt plus 4pt minus 2pt}{5pt plus 2pt minus 2pt} \titlespacing\subsection{0pt}{9pt plus 4pt minus 2pt}{2pt plus 2pt minus  2pt} \titlespacing\subsubsection{0pt}{9pt plus 4pt minus 2pt}{2pt plus 2pt minus 2pt} \setlength\parindent{0pt}  % Here the code of Christian Hupfer \usepackage{tocloft} \renewcommand\cftpartpresnum{\hfill} \renewcommand\cftpartleader{\hfill}  \begin{document} \tableofcontents \part{First part} \chapter{A first chapter} \chapter{A second one} \part{Second part} \chapter{A third one} \chapter{The last one} \end{document}


In what countries does 911 work as an emergency number?

911 is the North American standard. I was thinking in case something happens and one were to panic that it'd be good to know if dialling 911, in other countries where it is not the primary emergency number, is still set up to go through to emergency services.


If a tablet has been stolen, the sim card removed and been factory reset, is it possible, at all, to have it tracked?


Way to calculate the dangerousness level of volts+amps? (don't want to learn the hard way)

Is there a formula to calculate the dangerousness of amps, and volts? like watts, for example. Watts = Volts x Amps. Generally speaking, you could say wattage takes into account volts, and amps. I am working on a robot. And am using high power motors. I don't want to learn the hard way, by getting shocked. I need a formula, or at least a wattage chart, to see, where, on the dangerousness scale my electrical system is.  If I am touching a 1.2ft wire supplying 12v 80A of electricity, how fatal would that be (both heat wise, and shock wise), or would i be able to feel it at all?


Construct a bijection between $[1,2]$ and $[3,5)$.  So what I usually do if I pair the two outer number together to each other so like $3=1m+b$ and $5=2m+b$ and just solve for m and b but since 5 is not included, I am not sure how to construct it that makes it still a bijection. Thanks for any help!  Edit: this is not from $(0,1] \rightarrow (0,1)$ and also the brackets are different.


In C++/CLI, what does the hat character ^ do?

I was reading Ivor Horton's Beginning Visual C++ 2008 and many of its CLR examples have this definition for main:  int main(array<System::String ^> ^args)   I went back, page by page, to the beginning of the book to find the first such instance with an explanation what it really means, but couldn't find one.  Obviously it means the same as the standard int main(int argc, char *argv[]), but I'd like to know when and why that ^ is really used, and why it even exists (does it do something that pointers * and references & cannot represent)?


public class DataFactory {      class SYNOP implements IDataSources {}     class WRF implements IDataSources {}      public abstract class Factory {         public abstract IDataSources CreateModel();     }      public class SYNOPFactory extends Factory {          @Override         public IDataSources CreateModel() {             return new SYNOP();         }     }      public class WRFFactory extends Factory {          @Override         public IDataSources CreateModel() {                  return new WRF();         }            }      public static void main(String[] args) {          Factory factory = new WRFFactory();      } }   And i got message error like this:     No enclosing instance of type DataFactory is accessible. Must qualify   the allocation with an enclosing instance of type DataFactory (e.g.   x.new A() where x is an instance of DataFactory).   What did i do wrong?  Regards


Identifying which part of a large document is being compiled

I've a large document partitioned into several files and glued together with \input and \include. To improve detecting errors it would be quite helpful if everytime a new file is entered pdflatex would write an identification text. Is that possible and how? Thanks


Windows 10 lock screen requires that I press 'enter' or some other key before I can enter my password. If, as soon as I turn on the computer, I start typing my password the first character activates the password box rather than being the first character.   So... My question is: does anyone know how I can change this behavior? I want to just be able to type my password in, without having to press a key before doing so.  Thanks!


How can a speedbooster improve the light performance of a lens?

I have been reading couple of times now about those new  for mirrorless cameras. They are being reviewed as improving the low-light performance of a lens by one full stop.   In my knowledge, when you add elements to a lens, you would make the image not better, but rather worse. Can someone explain me how this works in general terms?


Shouldn't Leela's parents' mailbox say "Leela" instead of "Turanga"?

How did the writers not notice that the mailbox of Leela's parents says "Turanga," and not "Leela"?  Turanga Leela is Leela's proper name, with Leela being her surname, so shouldn't it follow that her folks would be the same?


I've made some strange experiences ever since I upgraded from Ubuntu 16.04 to 18.04: Small vertical red lines are occuring next to (random) letters in almost every word that is displayed in any program. This is kind of annoying, since it renders a text hard to read. Changing of fonts does not help. Does anyone know what might cause this problem and could give me a hint regarding a possible solution?  I would highly appreciate that.


Dependent variable not correlated with independent, but still a predictor in regression

My regression model uses 4 independent variables and 1 dependent variable.  When I plot the dependent variables against the independent variables, only one of them shows a correlation. However, the regression analysis splits out 4 coefficients.   I'm trying to figure out how a variable can have a coefficient and affect the dependent variable when there doesn't seem to be a correlation between the two.  How exactly does this work?  Any help would be appreciated. I've tried looking this up but I'm not sure what to search.  Thanks,  I'm analyzing the following variables:avg. session length, time on app, time on website, length of membership, yearly amount spent.  Time on App is seemingly not correlated    Regression shows the following coefficients:  Avg Session Length: 25.98  Time on App: 38  Time on Website: 0.19  Length of Membership: 61


I'm an Australian Citizen who has been invited to volunteer in the States for 3 1/2 months with a letter of invitation. I will not be getting paid, all food and accommodation are covered by them and anything else is from me. Can I use the B1/B2 visa?


How it this possible? Even if the gif is fake, the Mythbusters did it and with a large sail it really moves forward. What is the explanation?


Is there any way to augment the previous render?

I rendered my scene with 1000 samples and it is still looking grainy. I would like to pass another 1000 samples on top of this render result. When I start a new render Blender starts rendering the new image. Is it possible to tell Blender to reuse the result of the previous render and just run another set of samples on top of it?


Prove that there exist integers $a$ and $b$, so $am + bn = 1$.

When $m,n\in \mathbb{Z} $ and $a,b \in \mathbb{Z}$, show that there exist integers $a$ and $b$, so $am + bn = 1$ which also means $gcd(m,n) = 1$.  I tried proof through contradiction but I didn't succeed. Any suggestion would be helpful.


I am wondering how to type those kinds of symbols in LATEX. Please help me.      Thank you very much!


HowTo: Properly Use a Classname in register_activation/deactivation_hook

I'm using Composer PSR-4 to autoload classes, but when I try to call register_activation_hook using a classname if get the following error (same for register_deactivation_hook):   call_user_func_array() expects parameter 1 to be a valid callback,  class `Activation` not found   The Autoload portion of composer.json looks like so...   "autoload": {     "classmap": [],     "psr-4": {         "BlackOpz\\OOPBookPlugin\\Inc\\": "./src/inc"     },     "files": [         "src/support/exceptions.php"     ] },   ...which adds the following line to my vendor/composer/autoload_psr4.php file...       'BlackOpz\\OOPBookPlugin\\Inc\\' => array($baseDir . '/src/inc'),   My directory structure is like so...   oop-book-plugin  - assets    - composer (directory)    - filp (directory)    - kint-php (directory)    - psr (directory)    - autoload.php  - src    - css    - inc      - Activation.php      - Deactivation.php  - etc      - ...   My Activation.php looks like so...   /**  *  * @package     BlackOpz\OOPBookPlugin  * @wordpress-plugin  */ namespace BlackOpz\OOPBookPlugin\Inc;  class Activation {      /**      * Activate Plugin.      *      * @return void      */     public static function activate() {         flush_rewrite_rules();     } };   My Deactivation.php looks like so...   /**  *  * @package     BlackOpz\OOPBookPlugin  * @wordpress-plugin  */ namespace BlackOpz\OOPBookPlugin\Inc;  class Deactivation {      /**      * Deactivate Plugin.      *      * @return void      */     public static function deactivate() {         flush_rewrite_rules();     } };   My main class which looks like so...   // Load Composer Autoload. if ( file_exists( dirname( __FILE__ ) . '/assets/vendor/autoload.php' ) ) {     require_once dirname( __FILE__ ) . '/assets/vendor/autoload.php'; }  use BlackOpz\OOPBookPlugin\Inc\Activation; use BlackOpz\OOPBookPlugin\Inc\Deactivation;  // Instantiate the class. if ( ! class_exists( 'Book' ) ) {      /**      * OOP Book Plugin Class      */     class Book {          // This only works INSIDE the class with an instantiated class (below)         public function activate() {             Activation::activate();         }          // This only works INSIDE the class with an instantiated class (below)         public function deactivate() {             Deactivation::deactivate();         }     }      // The instantiated class.     $book = new Book();     $book->register();       // THIS WORKS     // register_activation_hook( __FILE__, array( $book, 'activate' ) );     // register_deactivation_hook( __FILE__, array( $book, 'deactivate' ) );      // THIS DOES NOT WORK     register_activation_hook( __FILE__, array( 'Activation', 'activate' ) );     register_deactivation_hook( __FILE__, array( 'Deactivation', 'deactivate' ) );  }


Does the light color spectrum and frequency matter for photosynthesis?

Do plants grow differently when given sun light, wolfram lamp, fluorescent light, LED light, infrared, ultraviolet, x-ray, unfocused laser and stroboscope?


How to test whether SSH has passwordless access without prompting for password?

I'm writing an unattended shell script that sets up a new server. Since I may run it multiple times, I want to check whether passwordless SSH access has already been set up. A command like  ssh newhost.example.com /bin/true  will exit successfully if the access exists, but if not, it will hang waiting for a password to be entered.  Is there a way to turn off the possibility of password access for such a command so that it will quickly fail if passwordless access is not yet set up?


A sine integral $\int_0^{\infty} \left(\frac{\sin x }{x }\right)^n\,\mathrm{d}x$

The following question comes from   post $$\int_0^{\infty} \left(\frac{\sin x }{x }\right)^n\,\mathrm{d}x$$ but now I'd be curious to know how to deal with it by methods of complex analysis. Some suggestions, hints? Thanks!!!  Sis.


do you know anyone who is over 30 years old, but got admission from top math grad school?

I am going to apply math grad schools this year. But, the problem is now I'm 30 years old.  Do you know anyone who is 30 or over 30, but got admission from top math grad school?


Didn't Understand Relationship - How To Find Child Relationship Name?

I have a many-to many relationship between three objects. LGFProducts, PartsinProducts, and Parts. PartsinProducts is the junction object. I want to be able to get data like the names of the parts that are related to the selected LGFProduct.   I understand that parent-child relationship can only traverse one level down while grandchild-grandpa can travel 5 levels at most. What is the parent-child or child-parent in a many-to-many relationship?  I assumed that I should be traversing upwards from Parts to the junction object partsinproduct and then LGFProducts? But my friend who is not a Salesforce expert but has knowledge in CS said that I should do a parent-child query (of LGFProducts to partsinproduct) to child-parent relationship query (PartsinProduct to Parts). Or perhaps both of these options are wrong and another is appropriate.   Also, I am having a little trouble traversing for custom objects. I understand that I need to append the letter r instead of c but get confused. For example, this is my attempt at a three level upward traversal that fails.   SELECT Id, Name, Parts__r.PartsinProducts__r,LGFProducts__r.Name FROM Parts__c   Also if three levels of upward traversal are needed, could one provide an example with custom relationships? As seen above, I am having difficulty successfully querying a three level upward traversal statement for custom objects.  This is my attempt at the parent-child relationship query of LGFProduct to PartsinProducts:  SELECT Name,   (     SELECT Name     FROM PartsinProduct__r   ) FROM LGFProduct__c    I am then given this error:


50 reputation for making comments is too high

In general I like the reputation system, but personally 50 seems too high to be able to comment on other people's answers. I want to contribute. I want to dabble a toe in the water. Yet my only options are: ask a question, or find a question that I can answer that doesn't already have a good, complete answer.  Often I see existing answers that I would happily comment on, to improve them. Starting a whole new answer seems like the wrong thing.  Just saying.


Dealing with ^ symbol in string format python pandas

Let's say I have the following df:  import pandas as pd  df = pd.DataFrame({'A':['1^','2','3'],                    'B':['1^','2','3'],                    'C':['1^','2','3']}) df      A   B   C 0   1^  1^  1^ 1   2   2   2 2   3   3   3   I want to remove the '^' from the entire dataframe, so I thought using the .replace() method would work:  cols_to_check = ['A','B', 'C'] df[cols_to_check] = df[cols_to_check].replace({'^':''}, regex=True)   However, this is the output:  df      A   B   C 0   1^  1^  1^ 1   2   2   2 2   3   3   3   Nothing happens! This works with any character other than the carat symbol and it's frustrating me. Here is an example:  df[cols_to_check] = df[cols_to_check].replace({'2':''}, regex=True) df       A   B   C 0   1^  1^  1^ 1            2   3   3   3   Why is the carat symbol so stubborn? Is there a way I can fix this? It would be really helpful. Thanks!


What to do when a user doesn't accept any answers?

I recently gave an answer (the one and only so far) and the OP stated in a comment that it works perfectly.  But he either upvoted nor accepted it.  I went to his profile and saw that he doesn't upvote or accept at all.  What can I do?  Flagging his question is a bad idea. Should I tell a moderator? But how?


How can I create a chart with three dimensions?

How can I create a chart like the one below (taken from ) in LaTeX:


What can be said about $\text{Rank}(C)?$

Assume that $A\in\mathbb{R}^{n\times k}, \ B\in\mathbb{R}^{k\times m}$   and that $\text{Rank}(A)=r, \ \text{Rank}(B)=s.$ What can be said   about $\text{rank}(C),$ where $C=AB?$   The only thing I can quickly see here is that $C\in\mathbb{R}^{n\times m}.$ I also know that $\text{Rank}(C)=\text{Dim}(V(C)).$ But what is the dimension of $C$ then?  The exam has a really messy solution where the answers are that the rank of $C$ is sometimes $=s$ and sometimes $=r$. I don't understand any of it.


Determinant of rank-one perturbations of (invertible) matrices

I read something that suggests that if $I$ is the $n$-by-$n$ identity matrix, $v$ is an $n$-dimensional real column vector with $\|v\| = 1$ (standard Euclidean norm), and $t > 0$, then $$\det(I + t v v^T) = 1 + t$$ Can anyone prove this or provide a reference? More generally, is there also an (easy) formula for calculating $\det(A + wv^T)$ for $v,w \in \mathbb{K}^{d \times 1}$ and some (invertible) matrix $A \in \Bbb{K}^{d \times d}$?


Check solution for $\lim_{n\to \infty}\int^1_0 f(x^n)dx\,$

For a continuous $f(x)$ on $[0,1]$ I need to calculate $\lim_{n\to \infty}\int^1_0 f(x^n)dx\,$   Let $\epsilon>0$ then,$\quad \int^1_0 f(x^n)dx\,=\int^{1-\epsilon}_0 f(x^n)dx\, +\int^1_{1-\epsilon}f(x^n)dx\,$, Applying mean value theorem $\exists c_1, c_2 $ such that $\int^{1-\epsilon}_0 f(x^n)dx\,=f(c_1^n)(1-\epsilon)$ and $\int^1_{1-\epsilon}f(x^n)dx\,=f(c_2^n)\epsilon$ , then $\lim_{n\to \infty}\int^1_0 f(x^n)dx\,=\lim_{n\to \infty} (f(c_1^n)(1-\epsilon)+f(c_2^n)\epsilon)=f(0)$


How can I detect inside a TeX file which engine (pdftex/xetex/luatex) is used to compile the file? Is there a LaTeX package that provides this functionality?


hibernate the computer for a given amount of hours

I am trying to set a wake/sleep cycle for my raspberry...  What I am trying to do is to wake it at ~ 6 am so that I can do some operations as I am about to wake up and to set it to hibernate once I am going to sleep at 22 pm.  While I know it's possible to hibernate at a specific hour I am not 100% sure how to wake it at a specific hour... or after x hours... does anyone know how to do this?  Edit: I am using ubuntu mate


/etc/grub.d/09_lowlatency and /etc/grub.d/10_linux double list kernel

In a fresh ubuntu-studio 14.04 install sudo apt-get install linux-generic.  Then the grub-mkconfig will give you a menu as such   Ubuntu (lowlatency) Ubuntu Advanced options for Ubuntu   A quick look with the 'e' key will show that both Ubuntu (lowlatency) and Ubuntu point to    linux   /boot/vmlinuz-3.13.0-24-lowlatency   A work around is you can select the desired kernel in  the 'Advanced option for Ubuntu' menu.  How can we fix /etc/grub.d/09_lowlatency and /etc/grub.d/10_linux so that they don't select the same default kernel?  Relevant menuentry in /boot/grub/grub.cfg from /etc/grub.d/09_lowlatency  menuentry 'Ubuntu (lowlatency)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-0f6e1051-cf9f-4299-b691-76d0d8c532d1' { recordfail         load_video         gfxmode $linux_gfx_mode         insmod gzio         insmod part_msdos         insmod ext2         set root='hd0,msdos1'         if [ x$feature_platform_search_hint = xy ]; then           search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1  0f6e1051-cf9f-4299-b691-76d0d8c532d1         else           search --no-floppy --fs-uuid --set=root 0f6e1051-cf9f-4299-b691-76d0d8c532d1         fi         linux   /boot/vmlinuz-3.13.0-24-lowlatency root=UUID=0f6e1051-cf9f-4299-b691-76d0d8c532d1 ro   quiet splash $vt_handoff         initrd  /boot/initrd.img-3.13.0-24-lowlatency }   And the menu entry in /boot/grub/grub.cfg from /etc/grub.d/10_linux  menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-0f6e1051-cf9f-4299-b691-76d0d8c532d1' {         recordfail         load_video         gfxmode $linux_gfx_mode         insmod gzio         insmod part_msdos         insmod ext2         set root='hd0,msdos1'         if [ x$feature_platform_search_hint = xy ]; then           search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1  0f6e1051-cf9f-4299-b691-76d0d8c532d1         else           search --no-floppy --fs-uuid --set=root 0f6e1051-cf9f-4299-b691-76d0d8c532d1         fi         linux   /boot/vmlinuz-3.13.0-24-lowlatency root=UUID=0f6e1051-cf9f-4299-b691-76d0d8c532d1 ro  quiet splash $vt_handoff         initrd  /boot/initrd.img-3.13.0-24-lowlatency }   Yes I assure you I have a normal kernel installed:  $ ls -l /vmlinuz* lrwxrwxrwx 1 root root 30 May  5 20:37 /vmlinuz -> boot/vmlinuz-3.13.0-24-generic lrwxrwxrwx 1 root root 33 May  2 20:25 /vmlinuz.old -> boot/vmlinuz-3.13.0-24-lowlatency


Prove there exist a $c$ such that $f'(c) = f(x_0)$

Suppose a function $f$ continuous on $[0,1]$ and differentiable on $(0,1)$ such that $f(0) = f(1) = 0$ and $x_0 \in (0,1) $. Prove that there exist $c \in (0,1)$ such that $f'(c) = f(x_0)$   My attempt:   Assume $f(x_0)>0$ there exist a $c_1$ such that $f'(c_1) = \frac{f(x_0)-f(0)}{x_0-0} = \frac{f(x_0)}{x_0} > f(x_0)$ as $x_0 <1$ and $c_2$ such that $f'(c_2) = \frac{f(1)-f(0)}{1} = 0 < f(x_0)$ by Mean Value Thereom and by IVT, there exist a  $c$ such that $f'(c) = f(x_0)$ Do the same for $f(x_0)<0$.   However, I realise that $f'$ may not necessarily be continuous which will cause IVT to not hold. What is the approach then?


Update a table with data from another table: truncated incorrect double value mysql

I have a Wordpress table in which I want to take the user_email from Table2 and import it to contact_email on Table1 one based off of the user_login. user_login and user_id equal the same value. Nothing I have tried has worked. Any thoughts? I receive truncated incorrect double value mysql when I run the   Table1    user_id|contact_email |contact_name  =======================================  123     |test@test.com |deft  124     |test3@test.com|deft3     Table2 (User table)   user_login|user_email     |display_name  =======================================  123       |test@test.com  |deft  124       |test3@test.com |deft3   I have tried:   update tbl1  join   tbl2  on     tbl1.user_id = tbl2.user_login  set    tbl1.contact_email = tbl2.user_email;   And received truncated incorrect double value mysql  and when I try:    update tbl1  join   tbl2  on     tbl1.user_id = tbl2.user_login  set    tbl1.contact_email = tbl2.user_email;  select * from tbl1;   I get 2 queries successfully executed. 0 record(s) were affected. There should be around 2000 records affected, so I know its not right.


Null space for $AA^{T}$ is the same as Null space for $A^{T}$

$A$ is an $n\times m$ matrix and $AA^{T}$ is a symmetric real matrix.  Also, we have: $\operatorname{rank}(AA^{T})=r\stackrel{?}{=}\operatorname{rank}(A)$.  Let $Q= \begin{Bmatrix} q_1,...,q_{n-r} \end{Bmatrix}$ be a basis for the Null space of $AA^{T}$. i.e. $AA^{T}q_i=0$, show that $A^{T}q_i=0$. I guess one proof can be that the Null space for $A^{T}$ is a subspace for Null space for $AA^{T}$, then the question would be why $\operatorname{rank}(A)=\operatorname{rank}(AA^{T})$?


Prove by induction, for all positive integers $n$, that $n!\ge2^{n-1}$

So far I have: Base case: $n=1$: LHS: $1!=1$, RHS: $2^{1-1}=1$, $1\ge1$ so $P(1)$ is true. Inductive step: Assume $n=k$ is true, that is $k!\ge2^{k-1}$, we must show that $n=k+1$ is true, that is $(k+1)!\ge2^k$. $(k+1)!=k!(k+1)\ge2^{k-1}(k+1)$ (since we assume $k!\ge2^{k-1}$)    Not really sure what to do after this, I know that $2^{k-1}=$$2^k\over2$ but I don't know if that helps at all.    Thanks in advance for any help!


Windows 10 and Ubuntu dual boot – Bootloader Question

I want to install Ubuntu on my Windows 10 machine. Last time I installed Ubuntu my PC was dead. Both Bootloaders were corrupted. What do I have to choose in the „Select Bootloader“ field? What do I have to do, if Ubuntu does not realize Windows. I saw some videos about dual boot, sometimes it shows: „Install with Windows“. Can I install Ubuntu on the same drive with Windows 10? I have two drives, do you recommend one for Win and one for Linux or is there no problem with two OSs on one drive?


What is an explicit formula for the seventh moment?

I am trying to perform an analysis using the seventh moment but I can't seem to find an explicit formula for anything past the fourth moment.  What is an explicit formula for the 7th moment similar to $\mu_1 =\frac{1}{N} \sum_i^N x_i$ for the mean ($1^{st}$ moment) and  $\mu_2 =\frac{1}{N} \sum_i^N \left( x_i - \mu_1 \right)^2$ for the variance ($2^{nd}$ moment)?


Can the knowledge of the inverse of $p$ modulo $q$ help factor $n=pq$?

With the RSA algorithm implemented using the Chinese Remainder Theorem (CRT), the private key has to be provided with not only $p$, $q$ and the private exponent $d$, but often also with the pre-computed value $q^{-1} \bmod p$ for a faster recombination using the CRT.  Assuming that $q^{-1} \bmod p$ is leaked to the adversary (but not $d$, $p$ and $q$ themselves), does that help factor $n = pq$? And if so, how?


How to edit a layer from a personal geodatabase in QGIS

I want to open and edit layers from a personal geodatabase in QGIS. I have read this  and I follow the ODBC way to open a personal geodatabase in QGIS with success.  However, I cant edit layers in QGIS.    The editing toolbar is grayed out.  Can I edit the layer from a personal geodatabase in QGIS? Is it possible ?


A more commonly understood synonym for "inculcation"

What word is similar to inculcation, but would be understood by ordinary people?  When I asked about inculcation, people didn't understand the word. Psychologists, however, use it.


Does the equation $𝑥^3+𝑦^3=3𝑧^3$ have any non-trivial pairwise co-prime integer solutions?

I´ve been assigned finding the non-trivial ($x+y\neq0$) solutions to this equation, if they exist. We have recently studied $\mathbb{Z}[\omega]$, where $\omega$ is a third root of unity. I tried factoring the equation into $$(x+y)(x+\omega y)(x+\omega^2y)=3z^3.$$ As I can suppose that $(x,y)=1$ because the equation is homogeneous, I could deduce that $x+y,x+\omega y$ and $x+\omega^2y$ have no common factors except maybe for the prime $1-\omega$, with exponent $\leq1$. We also know that $x+y$ is multiple of 3 (so, of $(1-\omega)^2$) looking at the equation mod 3 in the integers. And I could see too, using that $x\equiv1,y\equiv-1$ módulo 3, that $x+\omega y,x+\omega^2y$ are multiples of $\lambda$ but not of 3. So, as $(x+y)(x+\omega y)(x+\omega^2y)$ is 3 times a cube, I could express for some natural $n$ and $a,b\in\mathbb{Z}[\omega]$, with $a$ integer, and $u$ unit in $\mathbb{Z}[\omega]$: $$x+y=3^na^3\text{ (using that $x+y$ is an integer)}$$ $$x+\omega y=u(1-\omega)^mb^3$$ $$x+\omega^2y=\overline{u}(1-\omega^2)^m\overline{b}^3.$$ However I don´t know how to continue from here or if this is the right path. I searched a bit but didn´t find papers in English that explained a solution to this equation. Any help is appreciated :).


Querying MySQL table, records that include javascript. Single Quote Issue

The mysql table record:  definitionID = 1, term = alert('Hello World'); , definition = Javascript pop-up box   I am having some issues querying the definition field from the above example. Everything has already been through mysqli_real_escape_string as part of its form input method/validation.  The term is assigned to a variable earlier in my PHP. I think this worked fine.  //So, $term = alert('Hello World');  $definitionQuery="SELECT definition FROM definitionTable WHERE term='".$term."'"; $definitionArray = mysqli_query($dbc,$definitionQuery); $row = mysqli_fetch_array($definitionArray); $answer = $row['definition'];  /*In addition, document.getElementByID('test'); as a term doesn't work either but the following do. Gotta be something to do with single quotes but cant figure out what. Whilst the quotes are in a variable and not processed by PHP, might they be processed in mysql?*/  <script></script> or, document.getElementByID("DOUBLE");   The PHP error is:  mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given


System of Linear Equations - how many solutions?

For which real values of t does the following system of linear equations:  $$ \left\{  \begin{array}{c} tx_1 + x_2 + x_3 = 1 \\  x_1 + tx_2 + x_3 = 1 \\  x_1 + x_2 + tx_3 = 1 \end{array} \right.  $$  Have:  a) a unique solution?  b) infinitely many solutions?  c) no solutions?  I haven't done linear algebra in almost a year, so I'm really rusty and could use some pushes in the right direction.


We consider the following initial value problem for two functions $y(x),z(x)$:   \begin{align} 0&=y''+(y'+5y)\sin(z) \\ 5z'&=x^2+y^2+z^2 \end{align}   where $0≤x≤2$ and $y(0)=1.8$, $y′(0)=−2.4$, $z(0)=0.3$.      Approximate the solution of this initial value problem using Euler's method with $100$ steps. (Hint: Rewrite the system of ODEs in standard form using a suitable substitution)   I need to get the final ODE, then I can use Euler's method in maple. I just don't know how to get the correct equation.  Thanks!


Find the coefficient of $x^n$ simply by using binomial theorem

Find the coefficient of $x^n $ in the expansion of $\frac{1}{1-x+x^2-x^3}$.


Why did my question become Community Wiki?

I asked  on Stack Overflow, but after a few days it became Community Wiki. Why?   I think it is related to the number of editions of the question, but I'm not certain.


Why arguments of methods in java accept copy of references' address?

So this is a question about jvm design, since basically java is pass by value, and what is actually pass into method is object's reference address copy, then why we do that instead of passing the origin reference address? would this cause any trouble in practice? Thanks.


Reference Request: An introductory book on Kinetics, similar to Schroeder's on thermodynamics

I come from a statistics background and don't have much knowledge of physics. I need to gain bit of knowledge in statistical physics for one of the projects that I work on. I started looking at Reichl's and Kardar's book, but realized I needed some introductory material first on these topics.   Schroeder's book on thermodynamics was actually quite a nice introduction to that part of statistical physics. It explained a lot of the intuition behind the models as well as some of the formalism. I was wondering if anyone could suggest a similar type of introductory book for kinetics, meaning things like the Fokker-Planck equation, the Langevin equation, and the master equation, etc. I am just looking for something that provides a bit more explanation and intuition before I dive into the formalism.   Any suggestions would really be appreciated.


How do a black hole made from electrons produce EM field?

Imagine trillions upon trillions of electrons are squeezed into a tiny region of space creating a blackhole, how do this charged blackhole emit electromagnetic field? Hawking radiation do not count and assume no materials are falling in.


"This essay was translated from the Chinese" — what does this "the" do?

Chen Guangcheng is a special student at the U.S.-Asia Law Institute at   the New York University School of Law. This essay was translated from   the Chinese.   Why don't they write: "This essay was translated from Chinese"? (Omitting the "the" before "Chinese".)


Which is/are the most secure password hash algorithm(s) in PHP?

Which are the most secure password hash algorithm(s) in PHP?  Speed is irrelevant because I'm iterating the hash over a fixed time (rather than a fixed number of iterations). What I'm interested in is the mathematical strength.  My intuition tells me it's whirlpool, being the largest and slowest of the bunch. That or SHA-512. Which is recommended by experts?  Are there any other algorithms which provide more than 512 bit hashes?


Terminal displays directory of previous SSH location even when not running SSH

I am using the terminal app to ssh and when I do, it conveniently tells me (at the very top) what and where I am logged into for example:  user@computer:/home/user/directory/  and so forth. However, when I exit the ssh session and am sitting nicely at my local directory, it still tells me the directory path of the place I was previously logged in to.  Is there any way to have it tell me that information only when I am actually logged in to a remote machine? I have already gone to Terminal -> preferences -> profiles -> window and I only have "Dimensions" checked.


redirect all subdomains from http to https

I redirect all http requests for my subdomain to https by using following code.  <VirtualHost *:80>   ServerName subdomain.example.com   Redirect 302 / https://subdomain.example.com </VirtualHost>   Now my problem is how do I do it for all subdomains.  For example http:subdomain1.example.com should go to https:subdomain1.example.com and  http:subdomain2.example.com should go to https:subdomain2.example.com  How do I do it for all subdomains without having to create one virtualhost for all of them


How can I find the $\lim  (1+(a^{1/n}-1) / b)^n$ when $n \to \infty$?    I would greatly appreciate it if you kindly give me some hints.


Different mechanics of \hyperlink vs. \hyperref

I am fiddling around with the hyperref package to build a hypertext structure into my pdf. At first glance, hyperref provides two similar macros to put links between parts of my document: \hyperlink{target}{text} and \hyperref[target]{text}. You might notice their slightly different syntax. What really interests me is their different working mechanics. I will illustrate this by the following example: \documentclass{article}  \usepackage{pdfpages} \usepackage[]{hyperref} \usepackage{mwe}  \begin{document}  \section{Section Heading} \label{sectionheading}  \includepdf[link=true, linkname=pdfpage]{example-image}   Link to section works with \hyperref[sectionheading]{hyperref} and with \hyperlink{sectionheading}{hyperlink} (but with slightly different targets on the page).  Link to pdf works with \hyperlink{pdfpage.1}{hyperlink} but not with \hyperref[pdfpage.1]{hyperref} (and not this way, either: \hyperref[pdfpage]{hyperref}).  \end{document}  To link to the labeled section heading, I may use both commands. While \hyperref directs my pdf viewer directly to the linked section, \hyperlink directs me somewhere slightly different, so I can see more context. To link to the \includepdf of pdfpages however, I may only use \hyperlink. \hyperref does not work at all. I suspect this is because of a subtle difference in their working mechanisms. While checking the aux file, I found a line \newlabel{sectionheading}{{1}{1}{Section Heading}{section.1}{}} which \hyperref seems to use as a target. However, I did not find any similar target for the included pdf. My question: I suspect, I understand the workings of \label and \ref very well. \hyperref seems to work quite similarly with the added clickability. Could you please explain to me how \hyperlink does work differently and how it is implemented? E.g. what mechanics explain the difference when clicked on the link and where and how are the link targets stored in the first place?


Will an iron sphere covered all over with little neodymium magnets become a magnet monopole?

As iron reacts with magnets producing a field dependent on magnet's pole orientation should an iron sphere when covered with little magnets which nord poles aim towards the center of the sphere become nothing less than a monopole with spawning south poles lines outwards?


I'm trying to remember the name of a novel I read as a pre-teen.  If I recall correctly, it would have come out in the 90s (though it may have been a reprint).  The novel is set in modern times.  I recalled this because I've been reading a lot of urban fantasy lately, and this may be the first 'urban fantasy' book I read - our world, but with a touch of magic.  There's a somewhat clumsy, out of shape teenaged (or almost teenaged) boy who doesn't have a father.  His father had been a stage magician who was constantly frustrated by his son's complete inability to preform stage magic, despite a prediction saying he would have a great or powerful magic.  His father had died before the book started, I don't recall how long before.  The boy does something nice for an old woman (I don't recall what) and she gifts him a magical potion.  A drop of it, rubbed on his shoulder blades, will make him grow wings.  The book follows him for the summer, as he spends his evenings flying.  He makes himself a toga-like shirt out of some old curtains and spends time flying around at night.  I recall one scene where he learns about two children out in the middle of the bay (perhaps the book is set in San Fran?  I don't recall) in a rowboat with one oar.  He saves them (by pulling them back to shore using a rope they had with them) and gets mentioned in the paper as an angel.  At the end of the book, the potion has run out.  There's only a tiny little bit left, and when he rubs it in, it creates only a single feather.  Around that point, the boy realizes that he's no longer getting winded going up several flights of stairs and he's gained a lot of self-confidence.  From what I remember of the copy I read, the cover featured a shirtless boy wearing jeans standing in front of a mirror, looking at the large white feathered wings that had grown from his back.


Is it possible to read the request headers using Javascript in a Browser?

I have a S3 static page in a bucket and have added a Cloudfront distribution in front of it to access the webpage.  Now my question is: Is it possible to read the headers received by the webpage when the page is loaded? Is there a way I can print the headers on the webpage ?  Note: Im NOT about the response headers or the request headers before making a call from the client like mentioned over here:   Im asking the same question as over here:  for which there is no answer


Can you convert a neon RGB color to CMYK for printing?

I have a logo that was done with RGB colors, now I have to work with this logo to do something for printing purpuses, the problem is that in the RGB version of the logo I have a shade of green I cannot reproduce with CMYK... How do I do it?   I googled up a bit and found some CMYK values that would create a simmilar green, close enough, the problem is when I put those values in Illustratot(%C %M %Y %K) I don't get the color I am supposed to... what am I missing ?  I have an image to illustrate my problem :    The green I want to create in CMYK is the first green, when I put those values there I get the second green you see there, when I print this image will I get something close to the first green ? ...And this is simply how you view it on screen, a bit darked and washed up ? pom pomm pom pommmmmm  EDIT:  If I open up my logo in Photoshop and go to View > Gamut Warning the green part of my logo shows up in grey, to ged rid of the grey I lower the saturation, the problem is lowering the saturation ruins my nice bright neon green...    EDIT2:  If anyone around here printed neon green, how did you do it ?  I found on some forum someone saying that Pantone 802 C will print neon green, I looked it up, selected it and on screen it looks worse than my second green in the sample image... and anyway, putting a pantone color in a PDF that will be printed on a regular simple printer is any good  ?  [The material the logo will be printed on will be downloaded by various users over the internet in PDF format and will be printed by various home normal hobby printers, so I will not have the control over that at all, I just want a green that will print neon/led green or something closer on a regular hobby printer, not in some fancy color lab/printer. Its imposible isn't it ?]


how to search sqlite database record using for loop android

I want to loop through sqlite database if (johnny) is present in the database or not but my code is not working  if(!cursor.isAfterLast())  {     do      {         for(int i = 0; i<cursor.getCount(); i++)         {             if("johnny" == cursor.getString(1))             {                  Toast.makeText(getApplicationContext(), "string found!!! =)", Toast.LENGTH_LONG).show();             }         }                        }      while (cursor.moveToNext());     }            cursor.close(); }


Will my vote be valid if I only use one of the three in the moderator election?

This is the situation:  I'm not a very active user of Programmers SE. I know very few of the candidates, and though I've checked their profiles, I would feel irresponsible choosing three in some order. I have only seen one in action, and that person is the only one I'm "sure" could do a good job.  So, will my vote be valid?  The election page states:     Each community member has 3 votes. Please cast your votes in order of preference, starting with the most desirable candidate first.


Calculating average raster value for area in ArcGIS Desktop?

I have Raster data for a country which has Evaporation Data in its pixels. I also have Vector layer which has the 30 cities of the country.   What I need is the average Evaporation value of each city from the raster data using ArcGIS?  I have access to the spatial analyst extension.


max() not finding actual maximum value in list

I have two lists that i'm trying to split up so I can calculate the min and max values. The original list looks something like this:  vlim: [-6.44194488 -4.12189618] vlim: [-0.35109226  0.90269746] vlim: [-6.48470812 -4.06394711] vlim: [-0.35046298  0.89800871] vlim: [-6.50338849 -3.92795199]   and below you can see my script:  '''                                                                                Finding max and min vlim values                                                                                stars is lists[0] and gas is lists[1]                                                                                ''' from sys import argv  script, file = argv  with open(file) as f:     lists = ([], [])     for i, line in enumerate(f):         lists[i%2].append(line.strip())  ## stars ##                                                                                minlist = [] maxlist= []  for i in range(0,len(lists[0])):     min_tmp = lists[0][i][7:18]     max_tmp = lists[0][i][19:30]     minlist.append(min_tmp)     maxlist.append(max_tmp)  ## gas ##                                                                                minlist2 = [] maxlist2 = []  for i in range(0,len(lists[1])):     min_tmp2 = lists[1][i][7:18]     max_tmp2 = lists[1][i][19:30]     minlist2.append(min_tmp2)     maxlist2.append(max_tmp2)   print 'min star:  ', max(minlist) #max bc negative values                                                                                print 'max star:  ', min(maxlist) print 'min gas:   ', max(minlist2) print 'max gas:   ', max(maxlist2)   print'' print minlist print'' print minlist2 print '' print maxlist   I wanted to get rid of "vlim" and the brackets so I made two new lists; "minlist" which grabs the first number and "maxlist" which grabs the second. However, when I run max() on my gas list of maximum values, it doesn't pick out the actual maximum number:  min star:   -7.48815421 max star:   -3.84855181 min gas:    -0.97899559 max gas:    0.9262432]   But you can see in the list below that there's a few numbers larger than what max() found, see line 2:  [' 0.90269746', ' 0.89800871', ' 0.91088956', ' 0.92375575', ' 0.91859109', ' 0.91030079', ' 0.91962641', '0.9262432]', ' 0.93031583', ' 0.96124881', \ ' 0.97476199', ' 0.96566733', ' 0.96988751', ' 0.98140795', ' 0.96833185', ' 0.96395218', ' 0.9342977 ', ' 0.93163674', ' 0.89933621', ' 0.91770517', \ ' 0.92165692', ' 0.90245033', ' 0.89833043', ' 0.91639502', ' 0.88873233', ' 0.87241003', ' 0.78407889', ' 0.69231273', ' 0.63886276', ' 0.60207066', \ ' 0.58330105', ' 0.56990499', ' 0.55740021', ' 0.53945954', ' 0.51366063', ' 0.51928393', ' 0.46654584', ' 0.43496984', ' 0.39934928', ' 0.36126022', \ ' 0.32730902', ' 0.30790094', ' 0.28456324', ' 0.25893116', ' 0.24498652', ' 0.23020501', ' 0.20266526', ' 0.18111511', ' 0.16598142', ' 0.18298263', \ ' 0.15324247', ' 0.14616999', ' 0.11671082', ' 0.08299617', ' 0.04595069', ' 0.00824732', '-0.03321626', '-0.06159366', '-0.09449168', '-0.11242293', \ '-0.09726435', '-0.06395773', '-0.04232095', '-0.03196949', '-0.03847378', '-0.05006481', '-0.05253942', '-0.08344223', '-0.10788819', '-0.12003492', \ '-0.14036405', '-0.16807319', '-0.18165499', '-0.17822416', '0.1829591]', '-0.18755693', '-0.20039758', '-0.20103783']   Any idea how I can fix this? There's definitely something weird going on because I also had to use max() on "minlist2" (and min on "maxlist") to get it to give me the most negative number in the list (or smallest negative). Does it have something to do with the fact that there's both positive and negative numbers?  I'm really new to python so I may just be making some mistake in my script and not realizing it...  Sorry for the essay. Thanks!


I have been stuck on this problem for a really long time and it is due in a few hours. Let $A$ be a diagonalizable matrix and $λ$ an eigenvalue of $A$. Prove that $$rank(λI - A) = rank((λI - A)^2)$$ Hint 1: For any invertible matrix $B$, $rank(AB) = rank(BA) = rank(A)$. Hint 2: Diagonalize $λI - A$ and $(λI - A)^2$. Any help would be greatly appreciated. Thanks in advance! EDIT: Various people have pointed out that a similar thread was opened just recently. I went over and could only partially follow one of the suggested solutions - the others were beyond my level of understanding. In particular, this is the solution: Since $A$ is diagonalizable, A can be written in the form $A=PDP^{-1}$, then $rank(λI − A) = rank(λI−PDP^{−1}) = rank(P(λI − D)P^{−1}) = rank(λI − D)$. The person who suggested this solution also said that he made use of Hint 1 twice. Here is where I am lost. I understand that $rank(λI − A) = rank(λI − PDP^{−1})$, but how does $rank(λI − PDP^{−1}) = rank(P(λI − D)P^{−1}) = rank(λI − D)$? I do not even know how he made use of Hint 1 ): I apologise in advance to anyone who can take the trouble to explain this solution to me, if it is supposed to be trivial!


We’re considering an ideal opamp here; so does that mean that Vo is infinity ♾ * 0 (A * (V+ - V-))?   Thanks!


I feel that the brand tags such as  and  can be misused and create too broad of questions.  Should we remove these or put more stern wiki text for them?  As LBT has noted, this has been brought up before? Can we make an effort to remove these for good?


I need to calculate the time complexity of the following code:  for (i = 1; i <= n; i++) {   for(j = 1; j <= i; j++)   {    // Some code   } }   Is it O(n^2)?


Lower bound for complex polynomial beyond circle or radius R

If we have a polynomial with $c_i$ a complex number $$c_nz^n + c_{n-1}z^{n-1} + \cdots + c_1 z + c_0$$ then $$|P(z)| > \frac{|c_n|R^n}{2}$$ When |z| > R for some R  I have tried using the triangle inequality where I obtain, $|P(Z)| \leq |c_n||z|^n + \cdots + |c_0|$. But I seem to keep getting stuck. Any hints on how to move forward? Thank you!


Why only the year is as a link in \cite reference

I have a problem in citing references with \cite, I have only the year as a link. I want to display the author and year as a single link. I don't know where the problem is?!     \documentclass{article}    \usepackage{filecontents}%    %\usepackage[style=authoryear,natbib]{biblatex}    \usepackage[style=apa,backref=true,backend=biber,natbib=true,hyperref=true]    {biblatex}    \usepackage[american]{babel}   \DeclareLanguageMapping{american}{american-apa}    \begin{filecontents*}{apabibli1.bib}   @article{Sampson1989,   author = {Sampson, R J and Groves, W B},   year = {1989},   title = {Community structure and crime: testing social-disorganization theory},   volume = {94},   number = {4},   journal = {Am J Soc},   pages = {774}   }  @book{Rijsbergen1979,  author = {Rijsbergen, C V},  year = {1979},  title = {Information retrieval},  address = {London},  publisher = {Butter Worths}  } \end{filecontents*} \addbibresource{apabibli1.bib}   \renewcommand*{\labelnamepunct}{\addspace}   \usepackage{xpatch}   \xpatchbibmacro{author}  {%  \newunit\newblock   }   {%   \setunit{\addspace}\newblock    }{}{}    \xpatchbibmacro{name:apa:last-first}    {%    \addcomma\addlowpenspace\mkbibnamefirst{#3}\isdot    }  {%  \addlowpenspace\mkbibnamefirst{#3}\isdot  }{}{}  \renewbibmacro*{journal+issuetitle}{%  \usebibmacro{journal}%  \setunit*{\addspace\thinspace}%  \iffieldundef{series}  {}  {\newunit  \printfield{series}   \setunit{\addspace}}%    \printfield{volume}%   \printfield{number}%   \setunit{\addspace}\newblock    \usebibmacro{issuename}%    \newunit}    \AtBeginBibliography{\renewcommand*{\finalnamedelim}{%    \ifthenelse{\value{listcount}>\maxprtauth}    {}    {\ifthenelse{\value{liststop}>2}    {\addcomma\space}%    {\addcomma\space}}}}    \renewcommand\bibinitperiod{}    \renewcommand\bibinitdelim{}     \renewcommand\bibpagespunct{\addcolon\space}     \DeclareFieldFormat{journaltitle}{#1}      \DeclareFieldFormat[article]{volume}{\apanum{#1}}     \DeclareFieldFormat{title}{\iffieldequalstr{titleisdescription}{true}      {\mkbibbrackets{#1}}{#1\isdot}}     \renewcommand*{\finentrypunct}{\relax}   \setlength{\bibhang}{1.2em}   \usepackage[colorlinks]{hyperref}   \usepackage{hyperref}   \hypersetup{    colorlinks   = true,    citecolor    = blue,    linkcolor = blue,    urlcolor=blue    }    \begin{document}    \citealt{Sampson1989, Rijsbergen1979}\\    \citet{Sampson1989, Rijsbergen1979}\\    \citep{Sampson1989, Rijsbergen1979}\\    \citeauthor{Sampson1989}    \nocite{*}    \printbibliography    \end{document}


Do creatures summoned by a Planeswalker have summoning sickness?

has a loyalty ability which says:     Place three 1/1 white soldier creature tokens onto the battlefield.   When this ability is activated, do these soldiers have summoning sickness? I ask because Elspeth herself does not have summoning sickness when placed onto the battlefield.


let name; let hobbie; let occupation;  function setValue(aVariable, aValue){     aVariable = aValue; }  setValue(name, "John"); setValue(hobbie, "Travelling"); setValue(occupation, "Programmer");  console.log(name); // returns -> undefined console.log(hobbie); // returns -> undefined console.log(occupation); // returns -> undefined     How do I change the value of the global variables by a function?


Make a snapshot of Ubuntu for future installs

When we install Ubuntu, we get a lot of softwares pre-installed. Just like this, is it possible for me to install Ubuntu, then install all my required softwares and packages, setup my desktop and other system wide settings and once I get my perfect Ubuntu ready for use; I make snapshot or installable (my own Ubuntu version) of the system into a DVD or ISO. So that in future, I can just install Ubuntu through that ISO and get everything ready in a moment!  I checked , but remastersys is no longer available. I checked  as well, but it's too long and doesn't seem to be what I need.   Any other solution?


How can I rename a file in a different path without changing the current directory or writing the path twice?

For example, I want to rename tif/fat/tul/codes/MyCode.pl to TheCode.pl in the same directory. Currently I know I can use this:   mv tif/fat/tul/codes/MyCode.pl tif/fat/tul/codes/TheCode.pl   but that requires me to repeat typing the full path (can be annoying if the path is quite long)  or I can use   cd mv tif/fat/tul/codes/ mv MyCode.pl TheCode.pl   The drawback being I have to type 2 commands, and have to change the current directory is undesirable in many cases.  Is there a more efficient way to do this?


Is there a sandbox chat room for testing the API?

Right now I have one (1) reputation and I need 20 to be in a chat. How do I test the chat API? Do I need to get more upvotes to chat or is there a "sandbox" chat that does not need rep?  I know that the chat API is not formal and official and that is why I need to test it.  If there isn't a chat sandbox that doesn't require 20 rep, I will accept an answer saying so.


C# Winform: Setting the file save location

My program must produce files from some given data. I'm dealing with PDFs and Excel documents. How do I allow the user to set the directory where the files will be saved? I'm not referring to SaveFileDialog where the user must choose the directory every time.  I want the files to automatically be saved to the directory previously specified by the user. Something to this effect:    Most immediate solution I can think of is to store the directory in a file and read it every time a file is to be saved.  I also read about , but is it relevant to my case?


Is a polynomial of degree 3 with irrational roots possible?

It is easy to give an example of a polynomial of degree 3 with integer coefficients having:   (a) three distinct rational roots,  (b) one rational root and two irrational roots.  But for a while I am trying to construct one that all its roots are irrational but I can't. It seems that it is not possible at all?   Also, can a polynomial with integer coefficients of degree 3 have two rational roots and one irrational root?


British Mathematical Olympiad - December 2003 - Round 1 - Question 1

Here's the question.  Solve the simultaneous equations $$ab + c + d = 3$$ $$bc + d + a = 5$$ $$cd + a + b = 2$$ $$da + b + c = 6$$ where $a, b, c, d$ are real numbers.  Obviously there's a lot of ways to look at this, but I always find myselfat a dead end; either ending up with what I started with or getting a complicated mess. Is there a systematic way to approach this or is there just a niche technique required to answer this specific question? Also, is there a way of knowing before whether going through a method is going to provide new information of if I'm going to end up with something like $a=a$?


Unable to locate package -- when the /file/ is right in the directory (it's a .deb)

Guys: I'm tearing my hair out on this problem. I have 2 .deb files ready to install, and when I do sudo apt-get install *.deb I get: E: Unable to locate package discord-0.0.14.deb E: Couldn't find any package by glob 'discord-0.0.14.deb' E: Couldn't find any package by regex 'discord-0.0.14.deb' E: Unable to locate package XnViewMP-linux-x64.deb E: Couldn't find any package by glob 'XnViewMP-linux-x64.deb' E: Couldn't find any package by regex 'XnViewMP-linux-x64.deb'  My ls -lah shows: drwxr-xr-x  2 root    root    4.0K Mar 24 08:56 . drwxr-xr-x 10 root    root    4.0K Mar  2 20:57 .. -rwxrwxr-x  1 kcredden kcredden  69M Mar 24 08:54 discord-0.0.14.deb -rwxrwxr-x  1 kcredden kcredden  52M Mar 24 08:52 XnViewMP-linux-x64.deb  There was one fix that said some app wasn't installed, which I did and it fixed it then. But now I've got the same problem, so any help?     NAME="Ubuntu" VERSION="20.04.2 LTS (Focal Fossa)" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 20.04.2 LTS" VERSION_ID="20.04" HOME_URL="https://www.ubuntu.com/" SUPPORT_URL="https://help.ubuntu.com/" BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/" PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy" VERSION_CODENAME=focal UBUNTU_CODENAME=focal


Permission denied when using the terminal to install a program located in the download folder

roberto@roberto-870-224:~$ cd ~/Downloads roberto@roberto-870-224:~/Downloads$ ./daedalus-2.2.0-mainnet-14276.bin bash: ./daedalus-2.2.0-mainnet-14276.bin: Permission denied roberto@roberto-870-224:~/Downloads$


Question Gets Duplicated on a Different Q&A Site

My question gets cloned or duplicated on a different Q&A Site (not a different SE Site).  Question: No Microphone on CM12.1 Here's the , while here's the . It copied the exact same thing of my question / post, as well as the tags and the formattings; but it did not copy the edit / update and the comments (I can see no button there, to add a comment).  Thankfully, I searched / looked up my Question's Title. Upon looking at the site, it appears that they are also duplicating many other questions on SE (separated by  categories, located at the side / sidebar). Its welcome message says: (located at the upper part of the sidebar)  Welcome to Resdi Community, where you can ask questions and receive answers from other members of the community.  But, I did not post that on their "community", and I am not a member of their community.  I only post questions on Stack Exchange. I don't know if this is proper / right / legal, but they gave a credit to me.  They had put this:  asked Dec 29, 2016 in Android by Lloyd Dominic  But, what they don't give credit is that "This question came from Stack Exchange", or "This question is a copy of a question on Stack Exchange", or something similar to that ... Like I said, is this proper / right / legal?


how to distinguish using past simple or present perfect?

I wonder if there is any difference in meaning between these?  It’s years since I rode a bike. (it’s = it is)  It’s years since I’ve ridden a bike. (it’s = it is)   Thanks  In the following link, below the phrase Since and tenses, there is what I have already excerpted from:


Why is 75% code coverage required in Salesforce?

This might be a silly question, but I am new to Salesforce, so I am asking this question that why there is 75% code coverage concept is there in salesforce?  What I know, in order to deploy or create a package 75% code coverage is mandetory.  But why this percenatge concept is a very improtant aspect in salesforce.  Regards


What is the difference between max, min and sup, inf?


I am trying to prove the following theorems:  Let A, B, and C be nonempty sets and let $f : A \rightarrow B$ and $g : B \rightarrow C$.  If $g \circ f : A \rightarrow C$ is an injection, then $f : A \rightarrow B$ is an injection. If $g \circ f : A \rightarrow C$ is a surjection, then $g : B \rightarrow C$ is an surjection.   Any suggestions? Thanks!


What does "jam the speeders" mean, and is this used successfully in any other Star Wars media?

In The Rise of Skywalker, there's a point where Resistance fighters are performing an assault along the surface of a Star Destroyer, and Admiral Pryde reacts by telling a crew member to "jam the speeders". The crew member states that the Resistance members aren't using speeders, and it's revealed that they're riding horse-like animals for their assault.  Is there any explanation of what "jam the speeders" actually means, or what it would achieve, in any other Star Wars media (Legends or canon)?  Particularly, is there any example of it being used successfully at any point?


What is this dark copper-less PCB feature?

Excuse the title, I'm not even sure what to call it, as far as I can tell it isn't a component but a copper-less layer of PCB showing?  It's on a 'Zoom H1' microphone/recorder's PCB, as seen in . (As far as I noticed it didn't get a mention in the video.)


What is the difference between POST and GET?

I've only recently been getting involved with PHP/AJAX/jQuery and it seems to me that an important part of these technologies is that of POST and GET.  First, what is the difference between POST and GET? Through experimenting, I know that GET appends the returning variables and their values to the URL string  website.com/directory/index.php?name=YourName&bday=YourBday   but POST doesn't.  So, is this the only difference or are there specific rules or conventions for using one or the other?  Second, I've also seen POST and GET outside of PHP: also in AJAX and jQuery. How do POST and GET differ between these 3? Are they the same idea, same functionality, just utilized differently?


Let $C_o= \{(x_n):x_n \in R, x_n \rightarrow 0 \}$ and $ M=\{(x_n):x_n \in C_0,~~ x_1+ x_2+...+x_{10}=0\}$ then dimension of $(\frac{C_0}{M})$ is equal to


Is it bad to nullify objects in Finally?

I have seen developers have try, catch and finally in almost all the methods they write and they nullify the objects which they've created in the Finally block.  Eg-       public void Demo()      {         Something s = null;         try         {             s = new Something();         }         catch (Exception ex)         {              throw;         }         finally         {             s = null;         }      }   Is there any use of doing this? The propose of this is to nullify the object so GC can collect them.   Without doing this, Can we use a "using" or IDisposable instead?   What is the best practice?


Why does Copenhagen theme not support showing frame numbers?

I want to show Frame Number/Total Frame Number without navigation bar, just like the following picture:    The below MWE works as expect:  \documentclass{beamer} %\usetheme{Copenhagen}  \beamertemplatenavigationsymbolsempty \setbeamertemplate{footline}[frame number]{}  \begin{document}  \frame { \frametitle{Frame A} Frame A }  \frame { \frametitle{Frame B} Frame B }  \frame { \frametitle{Frame C} Frame C }  \end{document}   However, if I uncomment the second line %\usetheme{Copenhagen}, the Frame Number/Total Frame Number disappears as follows:    My compiler is TexLive 2018 with xelatex.  Is there any way to show Frame Number/Total Frame Number with Copenhagen theme?


Replacing ArcPy with ArcGIS API for Python?

Today I found out about the . I was wondering if you could use this to (eventually) replace ArcPy?  Recently I have been doing analyses that require cloud based solutions. When using AWS, Docker and Jupyter it is very convenient to stick with a Unix based OS such as Ubuntu. However, the Unix alternatives for ArcGIS have their own limitations as well such as the always hard to install python bindings for the  GDAL library. ArcGIS for Python operates cross platform.  Perhaps there are the things I should and should not expect from the ArcGIS API for Python.  Perhaps Arcpy is going to disappear altogether.


P.d.f of the absolute value of a normally distributed variable

I came across this question as an exercise, had a brief idea, but didn't know how to proceed.     Let $X \sim N(0, 1)$. What is the p.d.f of $|X|$ ?   I know the final p.d.f looks just like the right half of the original pdf, but extended vertically for a factor of 2.  Could someone please show mathematically what the p.d.f of variable |X| is going to be, and explain briefly? Thank you.


I tryed both ActionListener and Lambda for a jButton  but i am getting the below error:                                                                                AWT-EventQueue-0" java.lang.NullPointerException     at com.ibm.eNetwork.ECL.ECLPS.SendKeys(Unknown Source)     at com.ibm.eNetwork.ECL.ECLPS.SendKeys(Unknown Source)     at CI.SCMgrCEE.CustomActionListener.actionPerformed(CustomActionListener.java:157)     at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)     at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)     at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)     at javax.swing.DefaultButtonModel.setPressed(Unknown Source)     at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)     at java.awt.Component.processMouseEvent(Unknown Source)     at javax.swing.JComponent.processMouseEvent(Unknown Source)     at java.awt.Component.processEvent(Unknown Source)     at java.awt.Container.processEvent(Unknown Source)     at java.awt.Component.dispatchEventImpl(Unknown Source)     at java.awt.Container.dispatchEventImpl(Unknown Source)     at java.awt.Component.dispatchEvent(Unknown Source)     at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)     at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)     at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)     at java.awt.Container.dispatchEventImpl(Unknown Source)     at java.awt.Window.dispatchEventImpl(Unknown Source)     at java.awt.Component.dispatchEvent(Unknown Source)     at java.awt.EventQueue.dispatchEventImpl(Unknown Source)     at java.awt.EventQueue.access$500(Unknown Source)     at java.awt.EventQueue$3.run(Unknown Source)     at java.awt.EventQueue$3.run(Unknown Source)     at java.security.AccessController.doPrivileged(Native Method)   At the line 157 is the below:  psess.GetPS().SendKeys(String, 8, 18);   The String is a number that i got from an excel file.  What i am doing wrong?


Tangent to curve $x^3+y^3=a^3$ meets it again.


Is there a way to get an alphabetical list of abbreviations automatically? At the moment I have:  \begin{longtable}{ll}  APC & antigeen-presenterende cel \\  \end{longtable}   I use longtable because my table is very long.


I know two definitions of uniform integrability:   (Rudin - Real and Complex Analysis). Let $(X,\mathfrak{M},\mu)$ be a positive measure space. A set $\Phi\subset L^1(\mu)$ is called uniformly integrable if to each $\epsilon>0$ corresponds a $\delta>0$ such that $$\left|\int_E fd\mu\right|<\epsilon\tag{1}$$ whenever $f\in\Phi$ and $\mu(E)<\delta$. (Royden & Fitzpatrick - Real Analysis) Same thing except that $(1)$ is replaced by $$\int_E|f|d\mu<\epsilon.$$   Are the two equivalent? Clearly 2. implies 1., but I am not sure whether or not 1. implies 2.   The second one a lot more convenient to use in proofs, but sometime I don't know if "uniformly integrable" only assumes the first one.