Obtain the reduction formula for `intcos^(n)xdx`

Explanation

To derive the reduction formula for the integral \( I_n = \int \cos^n x \, dx \), we will use integration by parts. Here’s the step-by-step solution:

### Step 1: Set Up the Integral
Let \( I_n = \int \cos^n x \, dx \).

### Step 2: Use Integration by Parts
We can express \( I_n \) as follows:
\[
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