Buktikan sin 8A + sin 6A + sin 4A + sin 2A/ cos 8A + cos 6A + cos 4A + cos 2A = tan 5A

Pake rumus :
cos A + cos B =
2 {cos 1/2(A+B).cos 1/2(A-B)}
sin A + sin B =
2 {sin 1/2(A+B).cos 1/2(A-B)}