What is the integral of xcos(mx) ?

The integral of xcos(mx) is 1/(m^2)(mxsin(mx)+cos(mx))+C

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integral of xcos(mx)

\int x cos (m x) d x

\frac{1}{m ^{2}} (m x sin (m x) + cos (m x)) + C

Solution steps

\int x cos (m x) d x

Apply u-substitution

= \int \frac{u cos ( u )}{m ^{2}} d u

Take the constant out:

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

= \frac{1}{m ^{2}} \cdot \int u cos (u) d u

Apply Integration By Parts

= \frac{1}{m ^{2}} (u sin (u) - \int sin (u) d u)

\int sin (u) d u = - cos (u)

= \frac{1}{m ^{2}} (u sin (u) - (- cos (u)))

Substitute back

u = m x

= \frac{1}{m ^{2}} (m x sin (m x) - (- cos (m x)))

Simplify

= \frac{1}{m ^{2}} (m x sin (m x) + cos (m x))

Add a constant to the solution

= \frac{1}{m ^{2}} (m x sin (m x) + cos (m x)) + C

What is the integral of xcos(mx) ?
The integral of xcos(mx) is 1/(m^2)(mxsin(mx)+cos(mx))+C