Explain how to determine the value of x that gives a maximum for a transformed cosine function in the form y=acos(k(x-d)) + c, a>0, if the maximum for y=cosx occur at (0degrees, 1)
For maximum value, k(x-d) = 0 or a multiple of 2 pi.
One maximum is at x = d
Others will be at x = 2N*pi/k + d
where N is an integer.