9kosine(angel)...kommon trig funk=smooth kerv that go up & down
=the kommon "sine wave"
sins yu hav 9 in front, max value=9 & min =-9
kosine(0)=1, go down thru 0 at angel=90 deg, down tu -1 at angel=180 deg
next 180 deg=flip side...come bak up
kosine is symmetrik...kosine(-x)=kosine(x)