Prove that: `cos20^0cos40^0cos60^0cos80^0=1/(16)`

Explanation

To prove that \( \cos 20^\circ \cos 40^\circ \cos 60^\circ \cos 80^\circ = \frac{1}{16} \), we can follow these steps:

### Step 1: Rewrite the expression
We start with the expression:
\[ \cos 20^\circ \cos 40^\circ \cos 60^\circ \cos 80^\circ \]
We know that \( \cos 60^\circ = \frac{1}{2} \), so we can factor this out:
...