If my dad and grandma were both born in Canada but my grandfather was born in the US, does that mean I am part Canadian?    They are all US citizens and all my ancestors after my grandma came from other places.    If so how much would the percentage be?
My sister, cousins, and other relatives speculate that my mom's grandmother was Jewish (for various reasons). I've heard people say at times things like, for example, "I'm 50% German" or "I'm 25% Swedish." This has to do with their ancestry. But, how exactly is this calculated? Say for example that my mother's paternal grandmother was indeed 100% Jewish, what would that make me and my siblings, and how is it calculated?
Product of two cyclic groups is cyclic iff their orders are co-prime Say you have two groups $G = \langle g \rangle$ with order $n$ and $H = \langle h \rangle$ with order $m$. Then the product $G \times H$ is a cyclic group if and only if $\gcd(n,m)=1$.  I can't seem to figure out how to start proving this. I have tried with some examples, where I pick $(g,h)$ as a candidate generator of $G \times H$. I see that what we want is for the cycles of $g$ and $h$, as we take powers of $(g,h)$, to interleave such that we do not get $(1,1)$ until the $(mn)$-th power. However, I am having a hard time formalizing this and relating it to the greatest common divisor.  Any hints are much appreciated! Finding $\tan t$ if $t=\sum\tan^{-1}(1/2t^2)$ I am solving this problem. If $$\sum\limits_{i=1}^{\infty} \tan^{-1}\biggl(\frac{1}{2i^{2}}\biggr)= t$$ then find the value of $\tan{t}$.   My solution is like the following: I can rewrite: \begin{align*} \tan^{-1}\biggl(\frac{1}{2i^{2}}\biggr) &amp; = \tan^{-1}\biggl[\frac{(2i+1) - (2i-1)}{1+(2i+1)\cdot (2i-1)}\biggr] \\\ &amp;= \tan^{-1}(2i+1) - \tan^{-1}(2i-1) \end{align*}  and when I take the summation the only term which remains is $-\tan^{-1}(1)$, from which I get the value of $\tan{t}$ as $-1$. But the answer appears to be $1$. Can anyone help me on this. I have enabled storing Desktop &amp; Document Folders in iCloud. I keep my Xcode projects on Desktop. Every hour or so, iCloud will store files, inside of Pods folder present alongside the Xcode Project in iCloud. This is very tedious as I then have to click on each one of them one-by-one to re-download.  How can I prevent iCloud from downloading my files in this manner, for this specific Xcode project?  I have tried disabling iCloud for Desktop, but this results in me losing all my Desktop folders/files, so I could rather not go this route. (1) Does he not know? (2) Doesn't he know?  I don't usually see and hear questions formed in the first style. I was even surprised to know that it is grammatically correct. And actually it is the most &quot;proper&quot; way to form an interrogative sentence.  shows that the first style was much more popular before than now. What are your suggestions on choosing between these styles? And I will probably add the third one.  (3) He does not know?  EDIT: The answers have explained how to form a question, but have not actually provided an account on the usage of the first two forms. Especially I'm interested in the first form: does it sound formal, is it used in speech or only in writing, et cetera. Displaying mysql data in html table PHP Changing permissions on serial port I'm using the Arduino IDE in Ubuntu, and am having issues with the serial port. It has worked in the past, but for reasons that may be unnecesary, I felt the need to change the ownership of some of the files from root ownership to my users ownership.  This made the IDE work correctly, but I lost the ability to use the correct serial port.  In the dev folder, the port I need is listed as permission 166. Someone (who is no longer in the area to help me) swapped the permissions to 666, which made it all work gloriously.  However, it reverted back as soon as I restarted my computer, and if I now try to use the command:  sudo chmod 666 ttyACM0   nothing happens. No error messages, but no permission change either.    How can I change it, and how can I get it to change permanently.  I apologize if this question is overly simplistic or unclear, I'm an ubuntu noob, and I wouldn't begrudge feedback! iOS 7 Weather app expand/collapse transition jQuery/JavaScript: accessing contents of an iframe I would like to manipulate the HTML inside an iframe using jQuery.  I thought I'd be able to do this by setting the context of the jQuery function to be the document of the iframe, something like:  $(function(){ //document ready     $('some selector', frames['nameOfMyIframe'].document).doStuff() });   However this doesn't seem to work. A bit of inspection shows me that the variables in frames['nameOfMyIframe'] are undefined unless I wait a while for the iframe to load. However, when the iframe loads the variables are not accessible (I get permission denied-type errors).  Does anyone know of a work-around to this? Allow sound file uploads in questions and answers? Should Stack Exchange introduce the ability to upload embedded sounds (maybe via HTML5/Flash, whichever the user has) as part of questions and answers to Stack Exchange?  It could require a certain amount of rep to stop new users from doing it frivolously.  My rationale behind this is the new language &amp; usage sites.  I often find myself thinking that it might be helpful, when discussing a regional dialect or something, for the person answering to just pronounce what they're trying to describe in words. How can I undo git reset --hard HEAD~1? Is it possible to undo the changes caused by the following command? If so, how?  git reset --hard HEAD~1 What is the best way to iterate over a dictionary? trigger AccountReplicate on Account (after delete, after insert, after update) {     if ( trigger.isInsert ) {         for ( Account acc : trigger.new ) {             AccountOne__c ac = new AccountOne__c();             ac.Fax__c = acc.Fax;             ac.Phone__c = acc.Phone;             ac.Name =acc.Name;             insert ac;         }     }      if ( trigger.isUpdate ) {         integer  i = 0;         list&lt;AccountOne__c&gt; a2 = new list&lt;AccountOne__c&gt;([SELECT Id                                                         FROM AccountOne__c                                                         WHERE Name =: trigger.old[i].Name ]);         for ( AccountOne__c c1 : a2 ) {             c1.Name = trigger.new[i].name;             c1.Fax__C = trigger.new[i].Fax;             c1.Phone__C = trigger.new[i].Phone;             i++;         }         update a2;     } }   I tried bulk trigger for the update operation, but it's not working can anyone help me? I am attempting to set up an nmake makefile to export our balsamiq mockup files to png files automatically, but I'm afraid I can't make heads nor tails of how to make a generic rule for doing so, without explicitly listing all the files I want exported.  details the command line syntax for exporting the files, and  contains an example which looks like it contains a generic rule for .obj files to .exe files. The makefile I have tried so far looks like this: .bmml.png:     &quot;C:\Program Files\Balsamiq Mockups\Balsamiq Mockups.exe&quot; export $&lt; $@  But this doesn't work. If I simply run nmake (with some outdated png files), nmake just does this: [C:\Temp] :nmake  Microsoft (R) Program Maintenance Utility Version 9.00.30729.01 Copyright (C) Microsoft Corporation.  All rights reserved.   [C:\Temp] :  If I ask it to build one specific file, it does this: [C:\Temp] :nmake &quot;TestFile.png&quot;  Microsoft (R) Program Maintenance Utility Version 9.00.30729.01 Copyright (C) Microsoft Corporation.  All rights reserved.  NMAKE : fatal error U1073: don't know how to make '&quot;TestFile.png&quot;' Stop.  [C:\Temp] :  Any nmake gurus out there that can set me straight? An example makefile which simply makes .dat files from .txt files by copying them, to experiment with, looks like this: .txt.dat:     copy $&lt; $@  this does nothing as well, so clearly I'm not understanding how such generic rules work. Do I need to specify a goal above that somehow lists the files I want? I want to use $var in a shell brace expansion with a range, in bash. Simply putting {$var1..$var2} doesn't work, so I went "lateral"...   The following works, but it's a bit kludgey.    # remove the split files echo rm foo.{$ext0..$extN} rm-segments &gt; rm-segments source rm-segments   Is there a more "normal" way? How do you search for backdoors from the previous IT person? We all know it happens. A bitter old IT guy leaves a  into the system and network in order to have fun with the new guys and show the company how bad things are without him.  I've never personally experienced this. The most I've experienced is somebody who broke and stole stuff right before leaving. I'm sure this happens, though.  So, when taking over a network that can't quite be trusted, what steps should be taken to ensure everything is safe and secure? Antiresonance of multiple parallel decoupling capacitors: use same value or multiple values? My quesiton: Is it better practice to put same-valued capacitors in parallel of capacitors of different values to decouple the high-frequency noise caused by digital ICs? Background Digital IC need a decoupling capacitor close to their supply pins to ensure a stable voltage during power transients and to deal with noise (mostly to prevent noise generated by the IC to affect neighboring circuitry). It seems sensible to place a bulk capacitor (say 10-100uF), to act as an energy reservoir, and several smaller capacitors to deal with higher frequencies. The reason to place several small capacitors instead of just one is to deal with their Equivalent Series Inductance (ESL), which in practice, causes them to behave like an LC circuit. The effect of anti-resonance Yet, here is where best design practices and electronic myth seem to get mixed up and confusing to me. Most electronic engineers I have met like placing several decoupling capacitors of different values in parallel (with the smaller capacitors closer to the IC). The logic behind it is that the each capacitor takes care of a different noise frequency as depicted in Figure 1.  Figure 1: Impedance over frequency of three different value capacitors in parallel (cyan) vs their individual contribution (brown, blue, red). Image taken from . Note the small anti-resonance peak. It seams no major trouble , and the overall behavior of the three different capacitors in parallel is vastly superior to their individual decoupling capabilities. However, I have read in  by [Henry W. Ott] that placing capacitors of different values may cause a much greater antiresonance-peak which can be very harmful for our designs (see Figure 2). In fact, it amplifies any noise that falls into the anti-resoance frequency range, which is corroborated by .  Figure 2: from Electromagnetic Compatibility Engineering, by Henry W. Ott, section 11.4.4. The 15nH inductance makes reference to the capacitors ESL. How to have a one-to-many relationship with a privileged child? Question regarding an inequality How to prove that $$ \frac{x_1}{1+x_1^2}+\frac{x_2}{1+x_1^2+x_2^2}+\cdots+\frac{x_n}{1+x_1^2+\cdots+x_n^2}&lt;\sqrt{n} $$ knowing that $(x_n)$ is a positive sequence ? I looked up all kinds of inequalities such AM-GM, Chebyshev, Cauchy-Schwarz, but I couldn't manage to obtain anything useful.. Can anyone help ? Determining likely relationship based upon autosomal DNA shared cM Given two tests that share some cM of autosomal DNA, how can I easily find the predicted relationships that such shared cM would suggest? For example, a 2,200 cM match suggests it could be either: grandparent, half-sibling, or grandchild. If I enter the US by land, not needing ESTA, would I then need ESTA to enter by air 3 days later? I am a UK citizen, and therefore qualify for the USA's  (VWP). If I enter by  I need to apply for (and pay for) ESTA beforehand. If I enter by , I don't need ESTA. But I do get a 90 day visa waiver which allows me to go to Canada and return to the USA, on the same VWP.   My question is: If I first enter the USA on foot, from Canada (at Niagara Falls), return to Canada on foot, and then 3 days later fly from Canada into the USA, do I need ESTA? Or as my existing visa waiver is still in place, is that good enough?