# Homework Help: Find the mistake

1. Dec 16, 2006

### ddr

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

π^2
4
∫ COS(√x) dx
0

2. Relevant equations

3. The attempt at a solution

t=√x ; x=t^2 ; dx= 2t

π
2
∫ COSt · 2t dt = [SINt · 2t ] - ∫ 2SINt dt = π +2
0

yes but.. where is the mistake?
'cause the result is: π/2 - 1

thanx a lot

2. Dec 16, 2006

### cristo

Staff Emeritus
I get π +2. What makes you think the answer is π/2 - 1?

3. Dec 16, 2006

### neutrino

The answer should be $\pi - 2$. Check the substitutions in the final step.

4. Dec 16, 2006

### ddr

Neutrino is right, the result is π - 2, but why does the book report a π/2 - 1 result?

5. Dec 16, 2006

### neutrino

A typo, perhaps?