Question

Delta Cephei is one of the most visible stars in the night sky. Its brightness has periods of 5.4 days, the average brightness is 4.0 and its brightness varies by plus-or-minus 0.35. Find a formula that models the brightness, b, of Delta Cephei as a function of time, t, with t equals 0 at peak brightness

Answer 1

b = 4.0 + 0.35 cos (2 pi t/T)
where T is the period 5.4
use cos because it is +1, max at t = 0