The five points of y=sinx are (0,0), (∏/2, 1), (∏, 0), 3∏/2,-1, (2∏, 0) in turn.
The five points of y=cosx are (0, 1), (∏/2,0), (∏,-1), (3 ∏/2,0), (2∏,/kloc-.