If $\operatorname{cosec} \theta+\cot \theta=5$, then $\sin \theta=$
If $\operatorname{cosec} \theta+\cot \theta=5$, then $\sin \theta=$
- $\frac{1}{5}$
- $\frac{5}{26}$
- $\frac{5}{13}$
- $\frac{1}{13}$
Solution
Given $\operatorname{cosec} \theta+\cot \theta=5$
We know that $\operatorname{cosec}^{2} \theta-\cot ^{2} \theta=1$
$\Rightarrow(\operatorname{cosec} \theta-\cot \theta)(\operatorname{cosec} \theta+\cot \theta)=1 \Rightarrow \operatorname{cosec} \theta-\cot \theta=\frac{1}{5}$
Adding (1) \& (2), we get
$2 \operatorname{cosec} \theta=5+\frac{1}{5}=\frac{26}{5}$
$\therefore \operatorname{cosec} \theta=\frac{13}{5} \Rightarrow \sin \theta=\frac{5}{13}$
Asked in: MHT CET 2020 (14 Oct Shift 1)
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