# Thread: Integration by parts

1. ## Integration by parts

Hi. A troubling question I have here
Using integration by parts, show that if $I=\int\sqrt{1-x^2}dx$, that

$I=x\sqrt{1-x^2} -I + \int\frac{1}{\sqrt{1-x^2}}dx$

2. Thanks for the help, I didn't think of working it backwards. I'm just confused on one point

1) How does $\int\frac{1-x^2+1}{\sqrt{1-x^2}}dx$ become $\int\frac{-x^2}{\sqrt{1-x^2}}dx
$

3. ohh
i see there is a negative , I forget to enter it in the integral so

-1 +x^2 +1 = x^2