What is the integral of xcos^2(7x) ?

The integral of xcos^2(7x) is 1/392 (98x^2+14xsin(14x)+cos(14x))+C

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integral of xcos^2(7x)

\int x cos^{2} (7 x) d x

\frac{1}{392} (98 x^{2} + 14 x sin (14 x) + cos (14 x)) + C

Solution steps

\int x cos^{2} (7 x) d x

Rewrite using trig identities

= \int \frac{1}{2} x (1 + cos (14 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 x (1 + cos (14 x)) d x

Apply Integration By Parts

= \frac{1}{2} (x (x + \frac{1}{14} sin (14 x)) - \int x + \frac{1}{14} sin (14 x) d x)

\int x + \frac{1}{14} sin (14 x) d x = \frac{x ^{2}}{2} - \frac{1}{196} cos (14 x)

= \frac{1}{2} (x (x + \frac{1}{14} sin (14 x)) - (\frac{x ^{2}}{2} - \frac{1}{196} cos (14 x)))

Simplify

\frac{1}{2} (x (x + \frac{1}{14} sin (14 x)) - (\frac{x ^{2}}{2} - \frac{1}{196} cos (14 x))) : \frac{1}{392} (98 x^{2} + 14 x sin (14 x) + cos (14 x))

= \frac{1}{392} (98 x^{2} + 14 x sin (14 x) + cos (14 x))

Add a constant to the solution

= \frac{1}{392} (98 x^{2} + 14 x sin (14 x) + cos (14 x)) + C

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What is the integral of xcos^2(7x) ?
The integral of xcos^2(7x) is 1/392 (98x^2+14xsin(14x)+cos(14x))+C