For a Cosine function with amplitude = 0.75 and period = 10, what is y (4) ?

From my research, the cosine function is:

y (t) = Acos (ωt)

Where:

A = amplitude = 0.75

ω = angular velocity = (2*pi) / T = (2*pi) / 10 = 0.6283

Therefore:

y (4) = 0.75*cos (0.6283*4)

y (4) = 0.61