A Cepheid variable star is a star whose brightness alternately increases and decreases. Suppose that Cephei Joe is a star for wh
ich the interval between times of maximum brightness is 5.1 days. Its average brightness is 3.6 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)=3.6+0.55sin(2pi(t)/5.1)
I found the rate of change.. it's
0.677598cos(1.232t)
But, I also need to find the rate of increase after one day. (correct to two decimal places)
Time is being measured in days here so if you want to calculate the rate of increase after one day, substitute 1 for t in your rate equation: dB/dt = 0.677598 cos(1.232(1)) dB/dt = 0.22
