# How Many Times Do I Need To Integrate?

Calculus Level 5

$\large{\int_{0}^{\frac{\pi}{2}} \cos^n (\theta) \, d\theta}$

Find the value of the definite integral above, given that $n$ is an even positive integer. 

Notation: $\dbinom MN$ denotes the binomial coefficient, $\dbinom MN = \dfrac{M!}{N!(M-N)!}$.

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