`tantheta+tan2theta=tan3theta`

Explanation

To solve the equation \( \tan \theta + \tan 2\theta = \tan 3\theta \), we will follow these steps:

### Step 1: Rewrite the equation using sine and cosine
We start by expressing the tangent functions in terms of sine and cosine:
\[ \tan \theta = \frac{\sin \theta}{\cos \theta}, \quad \tan 2\theta = \frac{\sin 2\theta}{\cos 2\theta}, \quad \tan 3\theta = \frac{\sin 3\theta}{\cos 3\theta} \]
So, the equation becomes:
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