Let be a phase angle which is uniformly distributed over (0, 2. Suppose we form two

Let θ be a phase angle which is uniformly distributed over (0, 2π. Suppose we form two new random variables according X = cos (aθ) and Y = sin (aθ) to and for some constant a.
(a) For what values of the constant are the two random variables X and Y orthogonal?
(b) For what values of the constant are the two random variables X and Y uncorrelated?