If $\tan \theta+\sin \theta=a$ and $\tan \theta-\sin \theta=b$, then the values of $\cot \theta$ and…

If $\tan \theta+\sin \theta=a$ and $\tan \theta-\sin \theta=b$, then the values of $\cot \theta$ and $\operatorname{cosec} \theta$ are respectively
  1. $\frac{1}{a+b}, \frac{1}{a-b}$
  2. $\frac{2}{a+b}, \frac{2}{a-b}$
  3. $\frac{2}{a-b}, \frac{2}{a+b}$
  4. $\frac{1}{a-b}, \frac{1}{a+b}$

Solution

We have $\tan \theta+\sin \theta=a\ldots(1)$ and $\tan \theta-\sin \theta=b\ldots(2)$ Adding equation (1) \& (2), we get $2 \tan \theta=a+b \Rightarrow \tan \theta=\frac{a+b}{2} \Rightarrow \cot \theta=\frac{2}{a+b}$ By equation (1) - equation (2), we get $2 \sin \theta=a-b \quad \Rightarrow \sin \theta=\frac{a-b}{2} \Rightarrow \operatorname{cosec} \theta=\frac{2}{a-b}$

Asked in: MHT CET 2020 (14 Oct Shift 2)

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