Here are the questions:
I have posted a link there to this topic so the OP can see my work.Differential Equation 3.6?
Express the solution of the given initial value problem as a sum of 2 oscillations. Throughout, primes denote derivatives with respect to time t. Graph the solution function x(t) in such a way that you can identify its period.
2. x"+4x=5sin3t x(0)=x'(0)=0
4. x"+25x=90cos4t x(0)=0 x'(0)=90
Answer is x(t)=3/2 sin2t-sin3t and
x(t)=2√(106) cos(5t-alpha) + 10cos4t with alpha=pi-inverse tan(9/5) = 2.0779
I have no idea how to do this type of problem. Thank you for your help.