You can put this solution on YOUR website! General form:
y = a cos k(x-b)
where
amplitude is |a|
period is 2(pi)/k
phase shift is b
.
Your equation
y=3cos(2x-pi/2)
factor out the 2:
y=3cos 2(x-pi/4)
so, from inspection then
amplitude: 3
phase shift: (pi)/4
period:
(2(pi))/2
pi
