Hey all,(adsbygoogle = window.adsbygoogle || []).push({});

I've been working on learning to solve some PDE's. To do this I've been reading other people's tutorials. Here's one on the heat equation:

http://www-solar.mcs.st-and.ac.uk/~alan/MT2003/PDE/node21.html

This is pretty much the same as the others I've read on the heat equation, but it's explained farily well. However there are a few points I don't understand, and I was hoping someone might clarify them for me.

At 2.54 ([tex]k=-p^2[/tex]), what is [tex]p[/tex] and where did it come from?

2.57: What happened here? I see that at [tex]X(0)=0[/tex] and [tex]X(l)=0[/tex] to set boundary conditions... I also see that this step is involved in plugging in to find the constants of the equation [tex]X(x)=Acos(px) + Bsin(px)[/tex] but..... I'm lost

Finally, we get to 2.58 and everything explodes. Why a sigma? Generally for this type of problem don't we separate the variables into two ODEs, then BAM using some assumed equation forms solve for the constants and you have a solution? More or less?

Thanks a lot for any insight you can give,

-Jack Carrozzo

http://www.crepinc.com/

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# Homework Help: Heat Equation: Why Sigma?

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