Evaluate: `inttan(x-theta)tan(x+theta)tan2x\ dx`

Explanation

To evaluate the integral \( \int \tan(x - \theta) \tan(x + \theta) \tan(2x) \, dx \), we can follow these steps:

### Step 1: Rewrite \( \tan(2x) \)
We can express \( \tan(2x) \) in terms of \( \tan(x - \theta) \) and \( \tan(x + \theta) \). Using the angle addition formula for tangent, we have:
\[ \tan(2x) = \tan((x - \theta) + (x + \theta)) = \frac{\tan(x - \theta) + \tan(x + \theta)}{1 - \tan(x - \theta) \tan(x + \theta)} \]

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