
Mike D. answered 05/01/21
Effective, patient, empathic, math and science tutor
General equation is y = a cos b (x-c) + d
a = amplitude
2π/b is the period, so b = 2π/period
c is the phase shift
d is the vertical shift
So here a = 6, b = 2π/2, c = 3 , d = 0
So y = 6 cos π (x-3)
You can plot this on Desmos (make sure you are working in radians) and check this