How do you evaluate the integral int xsin(3x^2+1)xsin(3x2+1)?

1 Answer
Jan 20, 2017

intxsin(3x^2+1)dx=-1/6cos(3x^2+1)+Cxsin(3x2+1)dx=16cos(3x2+1)+C

Explanation:

I=intxsin(3x^2+1)dxI=xsin(3x2+1)dx

Let u=3x^2+1u=3x2+1, so du=6xcolor(white).dxdu=6x.dx.

I=1/6intsin(3x^2+1)(6xcolor(white).dx)I=16sin(3x2+1)(6x.dx)

I=1/6intsin(u)duI=16sin(u)du

I=-1/6cos(u)+CI=16cos(u)+C

I=-1/6cos(3x^2+1)+CI=16cos(3x2+1)+C