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Question: Answered & Verified by Expert
If $\sin x+\operatorname{cosec} x=3$, then value of $\sin ^{4} x+\operatorname{cosec}^{4} x$ is
MathematicsTrigonometric Ratios & IdentitiesMHT CETMHT CET 2020 (20 Oct Shift 2)
Options:
  • A 74
  • B 47
  • C 07
  • D 49
Solution:
2692 Upvotes Verified Answer
The correct answer is: 47
We have $\sin x+\operatorname{cosec} x=3$
$\therefore \sin ^{2} x+\operatorname{cosec}^{2} x+2 \sin x \operatorname{cosec} x=9$
$\therefore \sin ^{2} x+\operatorname{cosec}^{2} x=9-2=7$
$\therefore \sin ^{4} x+\operatorname{cosec}^{4} x+2 \sin ^{2} x \operatorname{cosec}^{2} x=49$
$\therefore \sin ^{4} x+\operatorname{cosec}^{4} x=49-2=47$

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