# Homework Help: Integral Substituion Rule

1. Jul 15, 2008

### jkeatin

1. The problem statement, all variables and given/known data

as 0 goes to a $$\int \sqrt x_{a^2-x^2} \ {dx}$$

2. Relevant equations

Substitution Rule

3. The attempt at a solution

I need help starting it, i dont understand at all

Last edited: Jul 15, 2008
2. Jul 15, 2008

### Dick

You could try a trig substitution. Does anything come to mind?

3. Jul 15, 2008

### jkeatin

sorry how do i put an x before the square root
its supposed to be there

4. Jul 15, 2008

### Dick

If you get into tex problems then just say it in words, i.e. integral from 0 to a of x*sqrt(a^2-x^2)dx. Is that what you mean? In that case try the even simpler substitution of u=a^2-x^2.

5. Jul 16, 2008

### Dick

Is this it?
$$\int_0^a x \sqrt{a^2-x^2} \ {dx}$$

6. Jul 16, 2008

### jkeatin

yeah thanks

7. Jul 16, 2008

### HallsofIvy

With that x dx, there is a very simple susbstitution.