What is the integral of sin(7x)sin(6x) ?

The integral of sin(7x)sin(6x) is 1/2 (-1/13 sin(13x)+sin(x))+C

integral of sin(7x)sin(6x)

\int sin (7 x) sin (6 x) d x

\frac{1}{2} (- \frac{1}{13} sin (13 x) + sin (x)) + C

Solution steps

\int sin (7 x) sin (6 x) d x

Rewrite using trig identities

= \int \frac{1}{2} (- cos (13 x) + cos (x)) d x

Take the constant out:

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

= \frac{1}{2} \cdot \int - cos (13 x) + cos (x) d x

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 cos (13 x) d x + \int cos (x) d x)

\int cos (13 x) d x = \frac{1}{13} sin (13 x)

\int cos (x) d x = sin (x)

= \frac{1}{2} (- \frac{1}{13} sin (13 x) + sin (x))

Add a constant to the solution

= \frac{1}{2} (- \frac{1}{13} sin (13 x) + sin (x)) + C

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What is the integral of sin(7x)sin(6x) ?
The integral of sin(7x)sin(6x) is 1/2 (-1/13 sin(13x)+sin(x))+C