Why don't animals need filtered water?
Are humans the only animal that requires "clean water"?
How to tell if mains voltage is on with microcontroller? I want to be able to tell if the mains voltage is on or off with an Arduino.   How could I do this safely with minimal components (or components from Radio Shack)? How do I use Conditional Formatting based on due dates in Excel 2013? I am trying to format cells in Excel 2013. I want the cells to get colored as green, yellow, and red based on how close they are with the target date (January 13, 2015 in this case).  I am unable to use conditional formatting as Excel says that relative formatting is not permitted within conditional formatting.   Target:   06-01-2015  01-01-2015 02-01-2015 03-01-2015 04-01-2015 05-01-2015 06-01-2015 07-01-2015 08-01-2015 09-01-2015 10-01-2015   If the date in the cell is more than 2 days of the target date, I want the cell to change color to Green. I used =DATEDIF($N12,$N$9,"d")&gt;=3 and the format changed to green.  If the date in the cell is exactly 2 days near the target date, I want the cell to change color to yellow. I used =DATEDIF($N12,$N$9,"d")=2 and the format changed to yellow.  If the date in the cell is within 2 days of the target date, I want the cell to change color to red. I used =DATEDIF($N12,$N$9,"d")&lt;2 and the format changed to red only for 5th and 6th January. Apparently, it does not recognize negative values.  How can I get this to match the required colors? Show an exponential function has a valid density. Given:  Let $X$ be exponential with parameter $\lambda$, that is   $$ f_X(x) = \begin{cases} \lambda e^{-\lambda x} &amp; \text{if }x&gt; 0, \\ 0 &amp;\text{for }x\leq 0. \end{cases} $$  where $\lambda&gt;0$ is called the rate of the distribution.  Question:  Show that this is a valid probability density function (pdf).  Attempt:  Need to show that  $$ f(x) = \int^{\infty}_{-\infty} \lambda e^{-\lambda x}\,  dx=1\\\\ $$ Thus, \begin{eqnarray*} f(x)&amp;=&amp;\int^0_{-\infty} \lambda e^{-\lambda x} \, dx+\int^\infty_0 \lambda e^{-\lambda x} \,  dx\\[8pt] &amp;=&amp;0+\int^\infty_0 \lambda e^{-\lambda x} \, dx \\[8pt] &amp;=&amp;\lambda\int^\infty_0 e^{-\lambda x} \, dx \\[8pt] &amp;=&amp;1 \end{eqnarray*}  The problem is that my professor just told me that I skip a step right before I derive $1$. Any insight?  EDIT:  Given the great feedback, here is the answer:  \begin{eqnarray*} f(x)&amp;=&amp;\int^{\infty}_{-\infty} \lambda e^{-\lambda x} dx=1\\\\ f(x)&amp;=&amp;\int^{\infty}_{-\infty} f_X(x)dx\\ &amp;=&amp;\int^{0}_{-\infty} 0\,\,\, dx+\int^{\infty}_{0} \lambda e^{-\lambda x} dx\\ &amp;=&amp;0+\int^{\infty}_{0} \lambda e^{-\lambda x} dx\\ &amp;=&amp;\int^{\infty}_{0} \lambda e^{-\lambda x} dx\\ &amp;=&amp;\int^{\infty}_{0} e^{-\lambda x} \Big(\lambda \,\,\,dx\Big)\\ &amp;=&amp;\int^\infty_0e^{-u} du\\ &amp;=&amp;-e^{-u}\Big|^{\infty}_0\\ &amp;=&amp;1-\lim _{x \to \infty} e^{-u}\\ &amp;=&amp;1\\ \end{eqnarray*} Is commitment necessary to participate in beta (as of June 2015)? There's this proposal for a new S.E. site which is about to enter the beta phase. It reads  This proposal is in: Commitment A successful site needs people to commit to use it. This proposal is 100% complete. Committed users will be invited to the private beta soon.  I'd like to participate in the beta but I don't want to commit (due to a full name being required). Will I be unable to participate in the beta if I don't commit? Why didn't the machine affect Bond in Spectre? Does editing still bump a question? Many times in the past I've edited a somewhat recent answer—say, from 30 minutes ago—and noticed that the concomitant question didn't bump to the top.  I just confirmed it with ; the question is currently sorted in the JavaScript page based on when it was asked, not my edit.  I've never made edits just to bump a question to whore rep—my original answer was wrong which was why I fixed it—but my understanding is that the CW self-edit trigger exists to prevent  edit-then-bump-then-score-rep—profit! activity.    If non-ancient edits no longer bump a question, should the self-edit CW trigger be brought inline with this?  Should an answer be made CW if you make 10 edits that actually bump the question?  and to avoid any implication of impropriety, I'm already capped on SO, so I'm not looking for any sort of "meta effect" on my answer Integral of the square of the normal distribution. Does someone know what the integral of the square of the normal distribution with standard deviation sigma over the range $-\infty$ to $+\infty$ is?  Thanks! Biblatex enumerating sorted bibliography (using authoryear-ibid style) How can I set biblatex to insert "1. " before first bibliography item and so on? The bibliography is sorted by author and the numbers are not meant to be used anywhere else. Can I change my flight dates after I get my Schengen visa? How do I keep Python print from adding newlines or spaces? In python, if I say  print 'h'   I get the letter h and a newline.  If I say   print 'h',   I get the letter h and no newline.  If I say  print 'h', print 'm',   I get the letter h, a space, and the letter m.  How can I prevent Python from printing the space?  The print statements are different iterations of the same loop so I can't just use the + operator. How to change default viewport shading in 2.8? Is it possible to change the default mesh color/shading in 2.8 to be more like 2.79? I'm finding it hard to see finer detail in 2.8. On the left is 2.8 and the right is 2.79 Disable ClearType (blurry fonts) in Internet Explorer 10 on windows 7 I've installed recently the latest Internet Explorer 10 and found out again what was my issue with the previous upgrade -- blurry fonts aka ClearType! Unfortunately there are some apps that use IE engine and thus all content there is blurry too :/  I know about  but unfortunately it seems that it is only for IE9. Is there any other solution to disable CT in IE10?  (and for clarity - I don't like CT, I've tried tweaking it but for me it's just blurry and case pain in my eyes no matter what I do... it's probably related to the low dpi of my monitor) The question is based on my theory from the recent manga chapter (Naruto 661):     Sasuke, when stabbed by Madara is the effect of Tsukuyomi from Sasuke.   Now, to prove my theory, is there an episode in manga/anime that Sasuke used Tsukuyomi? Rename Multiple files in unix I have multiple files whose names look like this  2313_ABCDEAUG2014_PQRST_0_.pdf 3244_ABCDEAUG2014_PQRST_0_.pdf 4234_ABCDEAUG2014_PQRST_0_.pdf   t want to rename the file in the following format.  AZ-2014-08-2313.pdf AZ-2014-08-3244.pdf   Please suggest. How do favored classes work in Pathfinder? I'm working on creating a half-elf paladin character for a Pathfinder game.  Full disclosure: this is the first time I've tried creating a character; I've used ones other people created before.  In the text, it mentions something about "favored classes" I believe.  What is this? Western Digital drive making beeping noise Top Answers in network profile shows incorrect score post of mine has a score of 13, but the  shows that it has 14:  This seems to be a recur of  bug; @Catija's  says it's been fixed.  Can we fix that (again)? Let $A$ be the $\mathbb{C}$-subalgebra of $M_4(\mathbb C)$ consisting of matrices of the form   \begin{pmatrix} * &amp; * &amp; * &amp; *\\ * &amp; * &amp; * &amp;*\\ 0 &amp; 0 &amp; *&amp;0 \\ 0 &amp; 0&amp;* &amp;* \end{pmatrix}   Then how would I find the Jacobson radical $J(A)$ of $A$?    I don't really understand finding the Jacobson radical of $\mathbb{C}$-subalgebras.  Any help on this would be greatly appreciated, thank you! What are the Windows A: and B: drives used for? In Windows you have a C-drive. Everything labeled beyond that is with the following letter.   So your second drive is D, your DVD is E and if you put in a USB stick it becomes F and the following drive G. And so on and so forth.  But then, what and where are A and B-drives? Why do some AC adapters and power supplies generate a whining noise, and what can I do about it?