Find the value of `cos 12^(@)+cos 84^(@)+cos 156^(@)+cos 132^(@)`

Explanation

To find the value of \( \cos 12^\circ + \cos 84^\circ + \cos 156^\circ + \cos 132^\circ \), we can use the sum-to-product identities for cosine. Let's break it down step by step.

### Step 1: Group the terms
We can group the terms as follows:
\[ (\cos 12^\circ + \cos 132^\circ) + (\cos 84^\circ + \cos 156^\circ) \]

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