In the below integral, given that $a$, $\sigma$, $\epsilon$ are constants, how do I pull them outside the integration sign? $$E =\int_{0}^{\pi}{\frac{a^2\sigma \sin\theta}{2\epsilon\sqrt{a^2-x^2-2ax\cos\theta}}d\theta}$$
In fact i need to show that $$E = \frac{a^2\sigma}{\epsilon x}$$