Question

What is the integral of `cos(theta)^2`?

Answer 1

`=1/2[phi + 1/2sin2phi] + C`

Explanation:

Use double angle formula

`cos2phi = 2cos^2phi - 1`

`therefore cos^2phi = 1/2(1+cos2phi)`

`int cos^2phi dphi = 1/2 int (1+cos2phi) dphi`

`=1/2[phi + 1/2sin2phi] + C`