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\hfill \thepage} %} \input{tcilatex} \begin{document} Use the method of separation of variables to show that the 1-D heat conduction problem: find $u=u(x,y)$ so that \begin{eqnarray*} \frac{\partial u}{\partial t}(x,t)-\alpha \frac{\partial ^{2}u}{\partial x^{2}}(x,t) &=&0,\;00 \\ u(0,t) &=&0,\;t\geq 0 \\ u(l,t) &=&0,\;t\geq 0 \\ u(x,0) &=&f(x),\;0\leq x\leq l \end{eqnarray*} has the solution \[ u(x,t)=\sum_{n=1}^{\infty }c_{n}\sin \frac{n\pi x}{l}\exp \left[ -\alpha \left( \frac{n\pi }{l}\right) ^{2}t\right] \] where \[ c_{n}=\frac{2}{l}\int_{0}^{l}f(x)\sin \frac{n\pi x}{l}dx. \] \end{document}