# Math Help - [SOLVED] general solution

1. ## [SOLVED] general solution

find the general solution of the given differential equation
u''+ $w^2$u=cos $w$t

I assumed U to be Acoswt+Bsinwt but it didn't work out.
u''+ $w^2$u=cos $w$t
What you found is the solution to $u''+ w^2 u = 0$. You have to add to this a particular solution of $u''+ w^2 u = \cos (wt)$.