(a) Suppose that x and y satisfy the following system of differential equations:
x¨ + 2y˙ - x = cos(ωt),
y¨ - 2x˙ - y = sin(ωt).
Find the second-order differential equation satisfied by the complex variable z = x + iy.
Find the general solution of this differential equation for all real values of ω ≠ 1. Hence, find, for all real values of ω ≠ 1, the solutions satisfying the conditions x = x˙ = y = y˙ = 0 at t = 0.
(b) For the system of differential equations:
x˙ = 2y,
y˙ = 3x - y,
find the stationary solution and sketch the phase diagram.
Verify algebraically that the stationary point is a saddle point and find the equation of the stable branch.