Prove that `(tan^2 (2theta)-tan^2 theta)/(1-tan^2 (2theta) tan^2 theta)=tan (3theta)tan theta`

Explanation

To prove the identity

\[ \frac{\tan^2(2\theta) - \tan^2(\theta)}{1 - \tan^2(2\theta) \tan^2(\theta)} = \tan(3\theta) \tan(\theta), \]

we will use trigonometric identities and properties of tangent.

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