Acepheid 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 6.5 days. its average brightness is 2.5 and the brightness changes by +/-0.45. using this data, we can construct a mathematical model for the brightness of cepheid joe at time t, where t is measured in days: b(t)=2.5+0.45sin(2πt/6.5) (a) find the rate of change of the brightness after t days. rate of change = equation editor equation editor (b) find the rate of increase after one day. rate of increase =