What is the integral of sin^3(2θ) ?

The integral of sin^3(2θ) is 8(-(cos^4(θ))/4+(cos^6(θ))/6)+C

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integral of sin^3(2θ)

\int sin^{3} (2 θ) d θ

8 (- \frac{cos ^{4} ( θ )}{4} + \frac{cos ^{6} ( θ )}{6}) + C

Solution steps

\int sin^{3} (2 θ) d θ

Rewrite using trig identities

= \int 8 cos^{3} (θ) sin^{3} (θ) d θ

Take the constant out:

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

= 8 \cdot \int cos^{3} (θ) sin^{3} (θ) d θ

Rewrite using trig identities

= 8 \cdot \int (1 - cos^{2} (θ)) sin (θ) cos^{3} (θ) d θ

Apply u-substitution

: \int - u^{3} (1 - u^{2}) d u

= 8 \cdot \int - u^{3} (1 - u^{2}) d u

Expand

- u^{3} (1 - u^{2}) : - u^{3} + u^{5}

= 8 \cdot \int - u^{3} + u^{5} d u

Apply the Sum Rule:

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

= 8 (- \int u^{3} d u + \int u^{5} d u)

\int u^{3} d u = \frac{u ^{4}}{4}

\int u^{5} d u = \frac{u ^{6}}{6}

= 8 (- \frac{u ^{4}}{4} + \frac{u ^{6}}{6})

Substitute back

u = cos (θ)

= 8 (- \frac{cos ^{4} ( θ )}{4} + \frac{cos ^{6} ( θ )}{6})

Add a constant to the solution

= 8 (- \frac{cos ^{4} ( θ )}{4} + \frac{cos ^{6} ( θ )}{6}) + C

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What is the integral of sin^3(2θ) ?
The integral of sin^3(2θ) is 8(-(cos^4(θ))/4+(cos^6(θ))/6)+C