If $\alpha+\beta=\frac{\pi}{2}$ and $\beta+\gamma=\alpha$, then $\tan \alpha$ equals

If $\alpha+\beta=\frac{\pi}{2}$ and $\beta+\gamma=\alpha$, then $\tan \alpha$ equals
  1. $2(\tan \beta+\tan \gamma)$
  2. $\tan \beta+\tan \gamma$
  3. $\tan \beta+2 \tan \gamma$
  4. $2 \tan \beta+\tan \gamma$

Solution

Given, $\alpha=\beta+\gamma$ $\begin{aligned} & \therefore \quad \gamma=\alpha-\beta \\ & \quad \begin{aligned} \tan \gamma & =\tan (\alpha-\beta) \\ & =\frac{\tan \alpha-\tan \beta}{1+\tan \alpha \cdot \tan \beta} \end{aligned} \end{aligned}$ $\begin{aligned} & =\frac{\tan \alpha-\tan \beta}{1+\tan \alpha \cdot \tan \left(\frac{\pi}{2}-\alpha\right)} \quad \cdots\left[\begin{array}{l} \alpha+\beta=\frac{\pi}{2} \\ \therefore \beta=\frac{\pi}{2}-\alpha \end{array}\right] \\ & =\frac{\tan \alpha-\tan \beta}{1+\tan \alpha \cot \alpha} \\ & =\frac{\tan \alpha-\tan \beta}{2} \end{aligned}$ $\begin{aligned} & \Rightarrow 2 \tan \gamma=\tan \alpha-\tan \beta \\ & \Rightarrow \tan \alpha=2 \tan \gamma+\tan \beta \end{aligned}$

Asked in: MHT CET 2024 (09 May Shift 1)

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