# Homework Help: Can someone please check my answer: Trig Substitution problem

1. Feb 26, 2009

### jimen113

I tried to use the latex reference but it was way too complicated for me.
Can you see the attachment.
Thank you!

#### Attached Files:

• ###### 7-3 problem 2.gif
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2. Feb 26, 2009

### HallsofIvy

If you are letting $x= cos(\theta)$ then $dx= cos(\theta)d\theta$. It looks to me like you forgot that $cos(\theta)$.

3. Feb 26, 2009

### jimen113

Thank you HallsofIvy for your help.
Yes it did forget! but wouldn't by dx= sin $$\vartheta$$
please see the updted the attachment.

#### Attached Files:

• ###### 7-3 problem 2 updated.gif
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125
4. Feb 26, 2009

### Staff: Mentor

If x = cos($\theta$), then dx = -sin($\theta$)d$\theta$

5. Feb 26, 2009

### HallsofIvy

Yes, of course Mark44 is right. I don't know what came over me!

6. Feb 26, 2009

### jimen113

Thanks Mark44! that negative sign is sure important...