They do not give me C they want me to find it. However I cannot find it this is what I have done
y=-4 cos (pi/6(1)-c)+77
-77=-4cos(pi/6-c)
19.5=cos(pi/6-c)
And this is where I am stuck really the problem claim it is a sinusoidal function if that help explain things.
But they gave me the amplitude, the vertical shift, and the period but they did not give me c or the phase shift so I guess they want me to find it inside the function.