Find all value of `theta`, between `0 & pi`, which satisfy the equation; `cos theta * cos 2 theta * cos 3theta = 1/4`.

Explanation

To solve the equation \( \cos \theta \cdot \cos 2\theta \cdot \cos 3\theta = \frac{1}{4} \) for \( \theta \) in the interval \( [0, \pi] \), we can follow these steps:

### Step 1: Rearranging the Equation
We start with the equation:
\[ \cos \theta \cdot \cos 2\theta \cdot \cos 3\theta = \frac{1}{4} \]
Multiply both sides by 4:
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