Solve: `cos2theta=cos^(2)theta`

Explanation

To solve the equation \( \cos 2\theta = \cos^2 \theta \), we can follow these steps:

### Step 1: Use the double angle identity for cosine
The double angle identity for cosine states that:
\[ \cos 2\theta = 2\cos^2 \theta - 1 \]
We can substitute this into our equation:
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