19. Consider the integral ∫cos(dr).
a) Using Euler's formula and equation (see formula sheet), rewrite cos into complex exponentials.
b) Using what you found above, evaluate the integral ∫cos(dr). Leave your answer in terms of complex exponentials.
c) Rewrite the integral as real-valued functions.
20. Use a strategy similar to above to evaluate ∫cos^3(x)cos(2x)dr.