Integration by Parts: Solving x^2(cosx)dx with Step-by-Step Guide

[ldbaseball16]

Homework Statement

solve by using intergration by parts x^2(cosx)dx

Homework Equations

My question is i got this answer but my computer algebra system gave me this answer
(x^2-2)sin(x)+2xcos(x) can you tell me where i went wrong??

The Attempt at a Solution

u=X^2
dv=cosx
du=dx
v=sinx

Sx^2(cosx)dx=uv-Svdu=x^2(sinx)-Ssinxdx

S2xcosxdx=2xsinx-(-cosx)+c= final answer= 2xsinx+cosx+C

 

[Dick]

If u=x^2, du=2x*dx. Not du=dx. You have to do integration by parts twice. And why are you integrating 2xcos(x)?

 

[ldbaseball16]

oo thank you