If U(t) = X cos t + Y sin t and V(t) = Y cos t + X sin t, where X and Y are independent RV’s such that E(X) = 0 = E(Y), E(X^2) = E(Y^2) = 1, show that {U(t)} and {V(t)} are individually stationary in the wide sense, but they are not jointly wide-sense stationary.