A few integration by parts problems

[kudoushinichi88]

Homework Statement

Hello. I am doing some problems on integration by parts and got stuck on the following problems. Any help would be appreciated.

i. \int \arcsin x dx

ii. \int_{0}^{1} x \ln (9+x^2) dx

iii. \int x^2 \arctan x\, dx

Homework Equations

u\,du=uv-v\,du

The Attempt at a Solution

i. I tried u= arcsin x and dv=dx, but ended up with an integral which looks worse than the original question.

ii. I used u= \ln (9+x^2)\,dx but ended up with

\int_{0}^{1} \frac{x^3}{9+x^2}\,dx
which I am stuck with.

iii. I tried u=arctan x and dv= x^2 dx but ended up with a similar looking integral in question ii, which is \int x \ln(1+x^2)\,dx

 

[Dick]

You are getting stuck at a point where a simple substitution would finish it. Look at ii). Try the u-substitution u=9+x^2.

 

[eumyang]

#1: you gave up too soon. Show us what you got.

#2: don't integrate by parts yet. Perform a u-substitution first.

#3: your choice for u and dv are fine, but I don't get that integral that's similar to #2. Again, show us what you got.

 

[hunt_mat]

For 1) look at the integral:
<br /> \int 1\cdot\sin^{-1}xdx<br />
Use u=arcsin x and dv=1