To prove the orthogonality of every two distinct functions in the sequence we must verify the following five claims: (a) (, sin na) = 0, ne N; (b) (, cos na) = 0, ne N; (c) (sin mx, cos na) = 0, m, n E N; (d) (sin mx, sin na) = 0, m #n, m, n E N; (e) (cos mx, cos na) = 0, m + n, m, n E N. %3D %3D %3D