We determine the complex-valued solutions of the following extension of the Cosine-Sine functional equation f(x sigma(y)) = f(x)g(y) + g(x)f(y) + h(x)h(y), x, y is an element of S, where S is a semigroup generated by its squares and is an involutive automorphism of S. We express the solutions in terms of multiplicative and additive functions.