# Homework Help: Volume by integration

1. Oct 27, 2005

### TSN79

I'm supposed to find the volume of the figure that appears by rotating the follwing around the x-axis:
$$y = e^x \cdot \sin (x) & x \in \left[ {0,\left. \pi \right]} \right.$$
This means (I think) that the function needs to be to the second power and multiplied by Pi in an integral. So the integral becomes
$$\pi \int {e^{2x} \cdot \sin ^2 (x)dx}$$
I need hints on how to solve this integral, I've tried integration by parts but not really gotten anywhere...am I on the right track?

2. Oct 27, 2005

### 1800bigk

here is a hint, maybe change sin squared into something more friendly.

Last edited: Oct 27, 2005
3. Oct 27, 2005

### TSN79

I tried to change it into 1-cos2x = 2(sinx)^2, but I didn't find it to make it any easier...was that what you thought about?

4. Oct 27, 2005

### 1800bigk

yes, change (sinx)^2 = 1/2 - (1/2)cos2x. multiply your e function through and you will have 2 integrals that can be solved. the integral with (e^2x)(1/2 cos 2x) is going to need parts twice.

Last edited: Oct 27, 2005
5. Oct 27, 2005

### TSN79

I do believe you might be on to something there 1800bigk...thx!

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