What is the integral of 4xcos(5x) ?

The integral of 4xcos(5x) is 4/25 (5xsin(5x)+cos(5x))+C

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integral of 4xcos(5x)

\int 4 x cos (5 x) d x

\frac{4}{25} (5 x sin (5 x) + cos (5 x)) + C

Solution steps

\int 4 x cos (5 x) d x

Take the constant out:

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

= 4 \cdot \int x cos (5 x) d x

Apply u-substitution

= 4 \cdot \int \frac{u cos ( u )}{25} d u

Take the constant out:

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

= 4 \cdot \frac{1}{25} \cdot \int u cos (u) d u

Apply Integration By Parts

= 4 \cdot \frac{1}{25} (u sin (u) - \int sin (u) d u)

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

= 4 \cdot \frac{1}{25} (u sin (u) - (- cos (u)))

Substitute back

u = 5 x

= 4 \cdot \frac{1}{25} (5 x sin (5 x) - (- cos (5 x)))

Simplify

4 \cdot \frac{1}{25} (5 x sin (5 x) - (- cos (5 x))) : \frac{4}{25} (5 x sin (5 x) + cos (5 x))

= \frac{4}{25} (5 x sin (5 x) + cos (5 x))

Add a constant to the solution

= \frac{4}{25} (5 x sin (5 x) + cos (5 x)) + C

What is the integral of 4xcos(5x) ?
The integral of 4xcos(5x) is 4/25 (5xsin(5x)+cos(5x))+C