I've put the ODE into a system.
which has Eigenvalues:
General Solution is
But this is where I am getting lost, I know that when the eigenvalues are complex I need to involve sin and cos, which is fine for a 1st order ODE but am getting a little stuck with this 2nd-order ODE.
Also, I need to find the solution in Real Form. i.e.
Thanks in advance to anyone who can help.