What is the integral of sin(x)*sin(nx) ?

The integral of sin(x)*sin(nx) is 1/2 (-1/(1+n)sin(x+nx)+1/(1-n)sin(x-nx))+C

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integral of sin(x)*sin(nx)

\int sin (x) \cdot sin (n x) d x

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

Solution steps

\int sin (x) sin (n x) d x

Rewrite using trig identities

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

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

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

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

Add a constant to the solution

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

(2 x - 1) d x + (5 y + 6) d y = 0

\frac{\partial}{\partial x} (x ln (\frac{x}{y}) + x y^{2})

\frac{c e ^{- a s}}{s ^{2}}

n = 2 \sum \infty e^{5 - 6 n}

\frac{d ^{3}}{d x ^{3}} (2 x)

What is the integral of sin(x)*sin(nx) ?
The integral of sin(x)*sin(nx) is 1/2 (-1/(1+n)sin(x+nx)+1/(1-n)sin(x-nx))+C