A Cepheid variable star is a star whose brightness alternately increases and decreases. For a certain star, the interval between times of maximum brightness is 6.6 days. The average brightness of this star is 3.0 and its brightness changes by +0.25. Using this information, the brightness of the star at time t, where t is measured in days, has been modeled by the function B(t)=3.0+ 0.25 sin 2xt $6.6 (a) Find the rate of change of the brightness at time t days. dB dt (b) Find the rate of change of brightness at time t = 1 day. dB dt =