# Integration question

1. May 29, 2013

### ZedCar

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

Could anyone please explain to me how the first integral in the attachment goes to the second?

Also, why the constant 'A' in the second is divided by 2?

'n' is an integer number.

Thank you.

2. Relevant equations

3. The attempt at a solution

#### Attached Files:

• ###### integral#.docx
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2. May 29, 2013

### slider142

They first use the half-angle identity $\cos^2(\theta) = \frac{1}{2}(1 + \cos(2\theta))$, and then use the fact that the cosine function has a period of 2π.

3. May 29, 2013

### ZedCar

Thanks slider142