Question

Integrate by parts ? 15x sinx dx

Answer 1

`-15xcos(x)+15sin(x)+c`

Explanation:

`int(15xsin(x))dx`

Since `sin(x)` is a periodic function, it is going to be `u'`

`u'=sin(x)" "u=-cos(x)`
`v=15x" "v'=15`

`int(v*u')=v*u-int(v'*u)`

`int(15xsin(x))dx=-15xcos(x)-int(-15cos(x))dx`
`-15xcos(x)+int(15cos(x))dx=-15xcos(x)+15sin(x)+c`