- #1
Dustinsfl
- 2,281
- 5
Solve inhomogeneous differential equation
\[
y'' + k^2y = \phi(x)
\]
with homogeneous boundary conditions \(y(\ell) = 0\) and \(y(0) = 0\) by expanding \(y(x)\) and \(\phi(x)\)
\begin{align*}
y(x) &= \sum_na_nu_n(x)\\
\phi(x) &= \sum_nb_nu_n(x)
\end{align*}
in the eigenfunctions of \(L = \frac{d^2}{dx^2}\) where \(Lu_n(x) = -k^2u_n(x)\) and \(u_n\) satisfies the homogeneous boundary conditions.
How am I supposed to use the definitions of \(y(x)\) and \(\phi(x)\) to solve this problem?
\[
y'' + k^2y = \phi(x)
\]
with homogeneous boundary conditions \(y(\ell) = 0\) and \(y(0) = 0\) by expanding \(y(x)\) and \(\phi(x)\)
\begin{align*}
y(x) &= \sum_na_nu_n(x)\\
\phi(x) &= \sum_nb_nu_n(x)
\end{align*}
in the eigenfunctions of \(L = \frac{d^2}{dx^2}\) where \(Lu_n(x) = -k^2u_n(x)\) and \(u_n\) satisfies the homogeneous boundary conditions.
How am I supposed to use the definitions of \(y(x)\) and \(\phi(x)\) to solve this problem?