Question

Can someone tell me how can it be like this?please upload detailed answer
http://imageshack.us/photo/my-images/843/dsc00441jz.jpg/

Answer 1

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Answer 2

Recall that
\(\cos(2x)=2\cos^2(x)-1\)
Plugin \(x=\theta/2\) we have \(1+\cos(\theta)=2\cos^2(\theta/2)\). When you take the square root of that you get \(\sqrt{2}\sqrt{\cos^2(\theta/2)}\) and then this the two square roots become \(2\) in the front of the integral.