- #1
raditzan
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Homework Statement
I have the solution to the heat equation, with the BC's and everything but the IC applied. So I am just trying to solve for the coefficients, the solution without the coefficients is
$$u(x,t) = \sum_{n=1}^{\infty} A_n\sin(nx)e^{-n^2t}$$
If the initial condition is ##u(x,0) = f(x)## such that $$f(x) = \begin{cases}
0 & 0 < x < \frac{\pi}{3} \\
100 & \frac{\pi}{3} < x < \frac{2\pi}{3} \\
0 & \frac{2\pi}{3} < x < \pi
\end{cases}
$$
I used the formula $$A_m = \frac{2}{\pi}\int_0^\pi f(x)\sin(mx)dx=\frac{200}{m\pi}\bigg[\cos(\frac{\pi}{3}m) - cos(\frac{2\pi}{3}m)\bigg]$$
I couldn't find a pattern in the coefficients other than all the even indices go to ##0##. Also is this even correct? When I try to graph this at ##t=0## it isn't giving me the piecewise function ##f(x)##. Is it just that I didn't use enough terms to make it noticeable? Also how would I show that at any time ##t>0## the temperature distribution in the rod achieves a local maximum at ##x=\pi/2##?
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