$$U_{tt} - c^2 U_{xx}= -g$$ where
BC: $U_{x}(0,t)=a\sin(ωt)$
IC: $U(x,0)=0$, $U_{t}(x,0)=0$
where $c, g, A$ and $ω$ are positive constants
Normally I wouldn't post for help here but I am absolutely desperate. I know how to solve this using the eigenvalue expansion method but I am absolutely terrible at Laplace and Fourier Transforms (Which i think i need to use one of the two).