Android Email EditText Validation
How should I validate an e-mail address?
Binomial confidence interval estimation - why is it not symmetric? I have used the following r code to estimate the confidence intervals of a binomial proportion because I understand that that substitutes for a "power calculation" when designing receiver operating characteristic curve designs looking at detection of diseases in a population.  n is 150, and the disease, we believe, is 25% prevalent in the population. I have calculated the values for 75% sensitivity and 90% specificity (because that's what people seem to do).      binom.test(c(29,9), p=0.75, alternative=c("t"), conf.level=0.95)      binom.test(c(100, 12), p=0.90, alternative=c("t"), conf.level=0.95)   I have also visited this site:    Which is a java page which calculates binomial confidence intervals, and it gives the same answer.  Anyway, after that lengthy set-up, I want to ask why the confidence intervals are not symmetric, e.g. sensitivity is      95 percent confidence interval:    0.5975876 0.8855583      sample estimate probability: 0.7631579    Sorry if this is a basic question, but everywhere I look seems to suggest that they will be symmetric, and a colleague of mine seems to think they will be too. So the complex number z is given as   $z=1-cos(2\theta)-isin(2\theta)$  And the question is to find the argument of z in terms of $\theta$.   So, I used the formula for calculating the argument of a complex number:  $arg(z)=arctan (\frac{sin(2\theta)}{1-cos(2\theta)})$  $=arctan (\frac{2sin\theta cos\theta}{1-(1-2sin^2\theta)})$  $=arctan (\frac{2sin\theta cos\theta}{2sin^2\theta})$  $=arctan (\frac{cos\theta}{sin\theta})$  $=arctan (cot\theta)$  $=arctan (tan(\frac{\pi}{2}-\theta))$  $=\frac{\pi}{2}-\theta$  But apparently the answer is $\theta-\frac{\pi}{2}$.  Where might have I gone wrong?  Edit: the domain given in the question for $\theta$ was $0≤\theta≤\pi$ When dragging an object, there is a greater start-up force than the force it takes to keep it moving. Why is this? Why are there two different values for friction? Can you say "are not we all?" instead of "aren't we all?" Because "aren't" translates to "are not" I pose the question, can you use both interchangeably (in the context of "aren't we all?")? "Are not" sounds very grammatically incorrect in this situation. Can you say "you need not go there" as opposed to "you needn't go there"?   Basically, I thought you can say "you need not" instead of "you needn't" but that you can't say "are not" instead of "aren't" (in the context I've provided) because I've never heard the second.  My friend believes that if you can use one example interchangeably, you can use the other as well.  So,   Can you use example '1' interchangeably? Can you use example '2' interchangeably? Let $x_n$ be a sequence of the type described above. It is not monotonic in general, so boundedness won't help. So, it seems as if I should show it's Cauchy. A wrong way to do this would be as follows (I'm on a mobile device, so I can't type absolute values. Bear with me.) $$\left|x_{n+1} - x_n\right| \leq \frac{1}{n^2}.$$ So, we have $$ \left|x_m -x_n\right| \leq \sum_{k=n}^{m} \frac{1}{k^2}$$ which is itself Cauchy, etc., etc. But, of course, I can't just use absolute values like that. One thing I have shown is that $x_n$ is bounded. Inductively, one may show $$ \limsup_{n \to \infty} x_n \leq x_k + \sum_{k=n}^{\infty} \frac{1}{k^2},$$ although I'm not sure this helps or matters at all. Thanks in advance.  Disclaimer I've noticed that asking a large number of questions in quick succession on this site is often frowned upon, especially when little or no effort has been given by the asker. However, I am preparing for a large test in a few days and will be sifting through dozens of problems. Therefore, I may post a couple a day. I will only do so when I have made some initial, meaningful progress. Thanks. In my Master thesis, I used this:  \begin{itemize}[label=\ding{167}] \item Access Windows XM from Ubuntu Server \item List the directories contents of Windows XP \end{itemize}   The output is:  My question: must I avoid the use of  such beautiful things when writing my thesis or is it a normal thing to do ? Most people with a degree in CS will certainly know what . It helps us to measure how well an algorithm scales.   But I'm curious, how do you calculate or approximate the complexity of your algorithms? I am using extensively trigonometric functions when an angle is given in degrees. Some of these functions like sine or cosine have rational values, for example, the well   known example is that $\cos(\theta) =0.6 $ and $\sin(\theta) =0.8 $.       However besides the case of multiplicity of $90^\circ$ it seems there are no rational numbers $\theta$  with simultaneously rational  values of  sine and cosine.      Is it possible somehow to prove that for rational values of an angle given in degrees there are  no values simultaneously rational of sine and cosine functions, beside obvious case of multiplicities of $90^\circ$? Three files have suddenly appeared in my home directory, called "client_state.xml", "lockfile", and "time_stats_log". The last two are empty. I'm wondering how they got there. It's not the first time it has happened, but the last time was weeks ago; I deleted the files and nothing broke or complained. I haven't been able to think of what I was doing at the time reported by stat $filename. Is there any way I can find out where they came from?  Alternatively, is there a way to monitor the home directory (but not sub-directories) for the creation of files? When umpire change the cricket ball, was the old ball thrown as waste or keep for reuse? I tried to install crossover and after downloading the .deb from their website, I followed the steps as indicated when opening it with Ubuntu Software Centre:     On 64-bit flavors of Debian and some Ubuntu variants, first open a   terminal and run sudo dpkg --add-architecture i386 ; sudo apt-get update   Since I have Ubuntu 16.04 LTS 64 bit I perform the command.  But when copying and pasting that command into my terminal, it stopped at Fetched 535kb in 7sec and stalled there for about 20 minutes. I ended up  closing it and tried to run both commands separately but after doing the sudo apt-get update command it also stalls again after "Fetched XXKb in XXsec."  I restarted my computer and decided to run the software updater and it stays stuck at roughly 75% for hours. My new laptop came preinstalled with Windows 8. Naively, as I am, I just formatted the harddrive and installed fine old Ubuntu. Now I want to install Windows 8 for dual boot again, but I have no DVD and do download the ISO one needs a product key. That key is not on the back of the laptop anymore but somewhere on the mainboard.  Is there any way to recover the product key from the mainboard using Ubuntu? Bring Debian to second Position in the GRUB Menu at startup Shouldn't rep gains from old questions & answers eventually stop (or at-least reduce)? "named" vs "that is named" I want to describe my business and want to refer to it in a sentence.  I am trying to say:      "In 2015 we established a business (that is) named X".   Intuitively, the "that is" part is redundant, and makes the sentence more cumbersome. But I cannot think of a reason why we should be able to drop the verb.  Is the version without the "that is" part grammatically correct? How can it be explained? I am writing a WP plugin. I have created a button for the user to click in thw WP dashboard. I need to run a function when a user clicks the button, shown with a red arrow. The code snippet for the button is:&lt;p&gt;&lt;button class="button button-primary"&gt;Update Media Titles and ALT Text&lt;/button&gt;&lt;/p&gt;. I have already created the function in my class like so:  public function kh_update_media_seo() {      //update media files title and alt tags here }   I can handle the code that goes in the function alone, I only need help making the button in the WP dashboard fire off this specific function when clicked.  Pardon me if this sounds dump or straight forward. It's my first time doing this.  My plugin is a one file plugin if that helps. Least expensive way to boost DC voltage What would be the least expensive way to boost a DC voltage?   The aim is to convert 1.2&nbsp;V/1.5&nbsp;V (from an AA/AAA cell) to 3.3&nbsp;V to power a small 8-bit microprocessor, like Atmel ATtiny45 or ATtiny2313, and also (if possible) 6&nbsp;V to power a buzzer.  Also, what would be the maximum current one could draw safely from an alkaline battery, after boosting it to 3.3&nbsp;V/6&nbsp;V?  Finally, how I could compute the duration for which the alkaline battery would last, given a certain consumption? If I run  export TEST=foo echo $TEST   It outputs foo.  If I run  TEST=foo echo $TEST   It does not. How can I get this functionality without using export or a script? Why are vias placed this way on a PCB? I used to check complex commercial PCBs specially those of graphics cards to see how professional PCB designers do their layout and learn from their techniques.  When I checked the card shown below I noticed two things regarding the placement of vias:  (A higher resolution image is ).   The PCB is surrounded by stitching vias all around the edges. What's the role of all of these? I think they're connected to ground to act as a shield, if that's true, I can't understand technically how by this placement they achieve this shield? By looking closer to the mounting holes, I noticed they added vias all around the pad, why? I accidentally set an object as camera, how do I undo this? I have a problem with rendering in cycles. In blender render my object is rendering fine, but in cycles when I pushed F12 I got only this:    One more thing: when I click 0 on keyboard I'm not in camera persp, but in object as camera, it looks like invisible layer, I don't know how to undo this, and be in camera persp again.  Does anybody have any idea how to fix this?