Answer:
-625
Step-by-step explanation:
The magnitude gets raised to the power, and the angle gets multiplied by the power:
5(cis7pi/4)^4 = (5^4)cis(4·7π/4) = 625cis(7π) = 625cis(π) = -625
We can split this up into 3 rectangles. 2 vertical ones (8 x 3) and one horizontal one in the middle (5 x (8 - 5)
8 x 3 = 24
24 x 2 = 48
5 x (8-5) = 5 x 3 = 15
now add 48 + 15 = 63 cm^2