# Homework Help: How to calculate this integral?

1. Jul 22, 2011

### athrun200

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

2. Relevant equations

3. The attempt at a solution
Can I use this substitution?

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2. Jul 22, 2011

### hunt_mat

Looks good, what does it come out to?

3. Jul 22, 2011

### athrun200

I am not sure for 2 things.

1. Since z is not a constant, does the derivative yield dz?
2. How can I write the range properly?

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4. Jul 22, 2011

### hunt_mat

You're fixing a point z and calculating the electric field there, the limits are easy, you have $L=\tan\theta$ and so the upper limit is $\theta =\tan^{-1}L$, the lower on is just 0.

Last edited: Jul 22, 2011
5. Jul 22, 2011

### athrun200

Thx!

6. Jul 22, 2011

### SammyS

Staff Emeritus
For your limits of integration look at your triangle. (The angle you labeled L is actually θ.) If x = 0, then sin θ = 0 and if x = L, then sin θ = L/√(L2+z2) .