Let A be the area if the region in the first quadrant under the graph of
y = cos(x) and above the line y = k for
0 < k < 1.
a. Determine A in terms of k.
b. Determine the value of A when k = 1/2
c. If the line y = k is moving upward at a rate of 1/pi units per minute, at what rate is the area A changing when k = 1/2?