Solve for variable y in terms of t W/ given initial condition:
dy/dt + 4y = 40sin3t y(0)=6
dy/dt + 4y = 40sin3t -----(1)
y will contain the Sin 3t and its derivative Cos 3t
Let y = C1*Sin 3t + C2*Cos ...
This shows how to solve for a variable with given initial conditions.