How to safely install Ubuntu alongside existing Windows 10?
How do I install Ubuntu alongside a pre-installed Windows with UEFI?
Photon energy - momentum in matter $E = h\nu$ and $P = h\nu/c$ in vacuum. If a photon enters water, its frequency $\nu$ doesn't change. What are its energy and momentum: $h\nu$ and $h\nu/c$ ? Since part of its energy and momentum have been transferred to water, it should be less.  If water's refractive index is $n$, are the energy and momentum equal to $h\nu/n$ and $h\nu/c/n$ ? How to make an ext4 formatted usb drive with full RW permissions for any linux machine? I want to format my USB stick to ext4 and just use as I would any other typical non-linux format drive (FAT32, exFAT, NTFS).   That is to say, I want to be able to plug the usb stick into any of my linux machines, and read/write to it without needing to adjust permissions, like doing chmod or chown stuff.  I would prefer to use GUI partition software like GParted, rather than command-line commands, though I welcome any solution!  I'm sure a post like this is duplicate flag heaven for some, but after browsing 6~10 SO and forum posts from google, I didn't find a simple solution to my question. Seemed like everything was about adjusting permissions on a per-user basis. Maybe you just cannot use ext4 drives with the same brainless convenience as NTFS. I'm looking for a quick start or template, or something, to get a web site's basic layout done quickly and looking fairly professional, and then let me do the coding.  I don't want a CMS, as this is for a highly customised reporting application, but I need something like frame header and two columns and frame footer.  I can design the pretty reports for the wide right hand column myself, as the left hand column menu. Selecting features with NULL attributes in QGIS How do I identify which features have NULL attributes in the attribute table of a shapefile?  When i try [field]= 'NULL' it selects the features with value = 0 (see picture) I wanted to tidy up a TeX document and was curious if you can use \lstinputlisting or a similar function to include a certain part of a source-code file.  Example, I have a 500 or so line source file and I want to include just lines 300-400.  Is there a way to do this? How to partition an encrypted disk Prove by Double Counting Method $\sum\limits_{k = 0}^m \binom{m}{k}\binom{n}{r + k} = \binom{m + n}{m + r}$ Show by combinatorial arguments that:   $$\sum_{k = 0}^m \binom{m}{k}\binom{n}{r + k} = \binom{m + n}{m + r}$$  Hello ,  I want to prove this argument by double counting method, i kinda have an idea of proving by comb args. but not by double counting... Can someone give any clues or ideas? thanks :) Should constructors comply with the Liskov Substitution Principle? I have an existing trigger which converts leads into peron accounts if the company name is blank.  Trigger AutoConvert on Lead (after insert) {      LeadStatus convertStatus = [           select MasterLabel           from LeadStatus           where IsConverted = true           limit 1      ];      List&lt;Database.LeadConvert&gt; leadConverts = new List&lt;Database.LeadConvert&gt;();       for (Lead lead: Trigger.new) {           if (!lead.isConverted &amp;&amp; lead.Company == null) {                Database.LeadConvert lc = new Database.LeadConvert();                String oppName = lead.Name;                 lc.setLeadId(lead.Id);                lc.setDoNotCreateOpportunity(true);                lc.setConvertedStatus(convertStatus.MasterLabel);                 leadConverts.add(lc);           }      }       if (!leadConverts.isEmpty()) {           List&lt;Database.LeadConvertResult&gt; lcr = Database.convertLead(leadConverts);      } }   I need to also write a trigger that stops records from coming into Salesforce if that email already exisits in a contact or an account (we use person accounts).  The issue is how do I get it working with the existing trigger (I need it to run before the trigger that converts it into a person account is run).   Is there a way to combine the two or add the functionality to create the record only if the email address doesn't already exist as a contact in the org? Are any of the USB ports on a Macbook Pro "always on" Always on USB ports will provide power to a device even when the laptop is shut down. Obviously this can be problematic for battery issues, but sometimes a user wants this capability all things considered.  Do the Macbook Pro offer this on any of the USB ports and if not is there any chance its wired and just has to be enabled? CSH - How to check if input is NOT number Need to apply it on csh.  to check if the inputted $2 is not number nor the word "all"  if ($#argv == 2 &amp;&amp; ($2 != all &amp;&amp; $2 != **any number**)) then    echo "wrong parameter" A line is drawn through the point $A(1,2)$ to cut the line $2y=3x-5$ in $P$ and the line $x+y=12$ in $Q$. If $AQ=2AP$, find the coordinates of $P$ and $Q$.  I found the lengths of the lines $AQ$ and $AP$ in terms of $x$ and $y$ and used $AQ=2AP$ to get this equation $11x^2-40x-16=0$  Working: $AP=\sqrt{(x-1)^2+(\frac{3}{2}x-\frac{9}{2})^2}=\sqrt{\frac{1}{4}(13x^2-62x+85)}$  $AQ=\sqrt{(x-1)^2+(-x+10)^2}=\sqrt{2x^2-22x+101}$  $AQ=2AP\Rightarrow \sqrt{2x^2-22x+101}=2\sqrt{\frac{1}{4}(13x^2-62x+85)}$  $\Rightarrow 2x^2-22x+101=13x^2-62x+85\Rightarrow 11x^2-40x-16=0$  Using the quadratic formula I found $x=4,x=-\frac{4}{11}$  I then substituted these values into the two equations in the question to get the coordinates $(4,\frac{7}{2}),(-\frac{4}{11},-\frac{15}{11})$ or $(4,8),(-\frac{4}{11},\frac{136}{11})$  But the answers in the book are $(4,\frac{7}{2}),(7,5)$ or $(\frac{2}{5},-\frac{19}{10}),(\frac{11}{5},\frac{49}{5})$  I don't know where I went wrong in my method.  Edit: Found some errors in my method and calculation.  Using $x=4$ in $2y=3x-5$ gives $P(4,\frac{7}{2})$  Line with points $AP$ has equation $y-2=\frac{\frac{7}{2}-2}{3}(x-1)\Rightarrow y=\frac{1}{2}x+\frac{3}{2}$  $Q$ lies on the same line. Therefore, the intersection between $y=\frac{1}{2}x+\frac{3}{2}$ and $y+x=12$ is the point $Q$. Working: $\frac{1}{2}x+\frac{3}{2}=-x+12\Rightarrow x=7$ Therefore, $y=-7+12=5$. Point Q has coordinates $(7,5)$.  But $x=-\frac{4}{11}$ is not the other $x$ coordinate of $P$ according to the answers in the book. I have no idea where I went wrong at this point. Command "find -name" must be enclosed in quotes or it doesn't work. Why is that? Objects not rotating with each other (Rubik's cube) How to construct a relative path in Java from two absolute paths (or URLs)? Given two absolute paths, e.g.  /var/data/stuff/xyz.dat /var/data   How can one create a relative path that uses the second path as its base? In the example above, the result should be: ./stuff/xyz.dat Saving memoization to disk In a Cartesian system, I've got the slope, start point and distance of a line segment.  What's the formula to find the endpoint? Why many abstract nouns get an indefinite article while it's taught that abstract nouns shouldn't get it? Getting key with maximum value in dictionary? Algorithm for computing Hadamard product of two rational generating functions If I have two generating functions $A(x) = \sum_na_nx^n$ and $B(x) = \sum_n b_nx^n$   then the Hadamard product is $(A \star B)(x) = \sum_{n} a_nb_nx^n$.  Now when $A$ and $B$ are both rational functions ($P(x)/Q(x)$ with polynomials $P, Q$) I've seen non-constructive proofs that $A \star B$ is also rational.  Given two rational generating functions $A$, $B$, is there an algorithm that efficiently computes $A \star B$? Or at least a constructive proof you could use to write an algorithm?