What is the integral of (cos(2θ))^2 ?

The integral of (cos(2θ))^2 is 1/2 (θ+1/4 sin(4θ))+C

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integral of (cos(2θ))^2

\int (cos (2 θ))^{2} d θ

\frac{1}{2} (θ + \frac{1}{4} sin (4 θ)) + C

Solution steps

\int (cos (2 θ))^{2} d θ

Rewrite using trig identities

= \int \frac{1}{2} (1 + cos (4 θ)) d θ

Take the constant out:

\int a \cdot f (x) d x = a \cdot \int f (x) d x

= \frac{1}{2} \cdot \int 1 + cos (4 θ) d θ

Apply the Sum Rule:

\int f (x) \pm g (x) d x = \int f (x) d x \pm \int g (x) d x

= \frac{1}{2} (\int 1 d θ + \int cos (4 θ) d θ)

\int 1 d θ = θ

\int cos (4 θ) d θ = \frac{1}{4} sin (4 θ)

= \frac{1}{2} (θ + \frac{1}{4} sin (4 θ))

Add a constant to the solution

= \frac{1}{2} (θ + \frac{1}{4} sin (4 θ)) + C

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What is the integral of (cos(2θ))^2 ?
The integral of (cos(2θ))^2 is 1/2 (θ+1/4 sin(4θ))+C