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यदि cosecθcotθ=72\operatorname{cosec} \theta-\cot \theta=\frac{7}{2}, cosecθ\operatorname{cosec} \theta का मूल्य

है:

a

4728\frac{47}{28}

b

5128\frac{51}{28}

c

5328\frac{53}{28}

d

4928\frac{49}{28}

Answer : Option C
Explanation :

cosecθcotθ=72\operatorname{cosec} \theta-\cot \theta=\frac{7}{2}

(i) cosec2θcot2θ=1\operatorname{cosec}^{2} \theta-\cot ^{2} \theta=1

cosecθ+cotθ=1cosecθcotθ=27..(ii) \Rightarrow \operatorname{cosec} \theta+\cot \theta=\frac{1}{\operatorname{cosec} \theta-\cot \theta}=\frac{2}{7} \ldots \ldots \text {..(ii) }

On adding both equations,

2cosecθ=72+272 \operatorname{cosec} \theta=\frac{7}{2}+\frac{2}{7}

=49+414=5314cosecθ=5328=\frac{49+4}{14}=\frac{53}{14} \Rightarrow \operatorname{cosec} \theta=\frac{53}{28}

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