C. If M is a closed subspace of a Hilbert space H, define the orthogonal complement of M to be M- = {x : (x, m) = 0 for all m EM}. (a) Show that every vector in H can be written uniquely as x = m +y, where m E M and y EM. Moreover, | |x| |2 = |/m| |2 + lly|12