State the transformation to the graph of either y=sinx or y=cosx that has occurred to result in each sinusoidal function.
a)y=-2cos(x/6) has a period of
6 units and is stretched vertically by a factor of 2.
b)y=sin(3x) has a period of 2π/3 and is compressed horizontally by a factor of 3.
c)y=cos(π/4-2x) has a period of π/2 and is translated horizontally π/8 units to the right.