Evaluate: `int_0^(2pi)cos^5x\ dx`

Explanation

To evaluate the integral \( \int_0^{2\pi} \cos^5 x \, dx \), we can follow these steps:

### Step 1: Rewrite the Integral
We start with the integral:
\[ I = \int_0^{2\pi} \cos^5 x \, dx \]
We can express \( \cos^5 x \) as \( \cos^4 x \cdot \cos x \).
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