4. A variable star is one whose brightness alternately increases and decreases. For the variable star Delta Cephei, the time between periods of maximum brightness is 5 days. The average brightness (...

Extracted text: 4. A variable star is one whose brightness alternately increases and decreases. For the variable star Delta Cephei, the time between periods of maximum brightness is 5 days. The average brightness ( or magnitude) of the star is 4 and its brightness varies by ±O.35 magnitude. Suppose the brightness of the star can be modeled by the equation y = a cosbt +d. a. What is the value of b? b. Find a function that models the brightness of Delta Cephei as a function of time.