A Cepheid variable star is a star whose brightness alternately increases and decreases. Suppose that Cephei Joe is a star for which the interval between times of maximum brightness is 4.7 days. Its average brightness is 3.2 and the brightness changes by +/-0.55. Using this data, we can construct a mathematical model for the brightness of Cephei Joe at time t, where t is measured in days:
B(t) = 3.2 + 0.55sin(2pit/4.7)
Find, correct to four decimal places, the rate of increase after one day.

Question

A Cepheid variable star is a star whose brightness alternately increases and decreases. Suppose that Cephei Joe is a star for which the interval between times of maximum brightness is 4.7 days. Its average brightness is 3.2 and the brightness changes by +/-0.55. Using this data, we can construct a mathematical model for the brightness of Cephei Joe at time t, where t is measured in days:
B(t) = 3.2 + 0.55sin(2pit/4.7)
Find, correct to four decimal places, the rate of increase after one day.