Wikipedia:Reference desk/Archives/Mathematics/2017 November 1

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November 1

Solution of a first order partial differential equation

I am looking for the solution of a first order partial differential equation: x du/dx + 2y/5 du/dy = 0 With the initial condition: u(x,0) = 5π/4

The particular solution should give: For x=16 and y=4, cos(2u/5) = 1/2 ; For x=16√3 and y=4, cos(2u/5) = 1/4⁡ ; For x=80√5 and y=4, cos(2u/5) = 1/6⁡ ; Thank youAcspor (talk) 05:17, 1 November 2017 (UTC)

Please do your own homework.

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. --Trovatore (talk) 05:46, 1 November 2017 (UTC)

Best practices to line up equals signs in a series of calculations

I am wanting to write a series of calculations and I want to be able to write it so the equal signs line up. The only thing I can think of is using a { | or { {table } }. What is the best way to do this? e.g.

y	= 2(x - 5)2
	= 2(x2 - 10x + 25)
	= 2x2 - 20x + 50

Nutster (talk) 18:20, 1 November 2017 (UTC)

Try alignat{} (Help:Displaying_a_formula#Fractions, matrices, multilines)

   <math>\begin{alignat}{3}
   y & = 2(x - 5)^2 \\
     & = 2(x^2 - 10x + 25) \\
     & = 2x^2 - 20x + 50
   \end{alignat}</math>

gives

${\begin{alignedat}{3}y&=2(x-5)^{2}\\&=2(x^{2}-10x+25)\\&=2x^{2}-20x+50\end{alignedat}}$

--catslash (talk) 23:08, 1 November 2017 (UTC)

Probably better to just use \begin{align} for simple alignments like above. This assumes you're actually doing stuff inside a <math></math> block, but if you're writing multiline equations like this, that's probably best anyway. alignat can do weird things with spacing if you're not careful (like it did above with the equals sign). Compare:

${\begin{aligned}y&=2(x-5)^{2}\\&=2(x^{2}-10x+25)\\&=2x^{2}-20x+50\end{aligned}}$

--Deacon Vorbis (talk) 23:28, 1 November 2017 (UTC)