y=4*sine(2x-pi/4)...start with standard sine kerv . . . 4* tell yu the up-down is tween -4 & +4 insted av -1 & +1 . . . then pi/4=45 deg...the kerv is offset LEFT 45 deg . . . normally, sine(0)=0, but wen x=0, yu hav sine(-45 deg) . . . sine(2x) tell yu it go up & down twice as fast as normal sine wave. . . . a full cycle take angel from 0 tu 360 deg, but heer, yu get 360 deg . . . wen x=180