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Question: Answered & Verified by Expert
The value of $\cos ^{-1}\left(\cos \left(\frac{7 \pi}{6}\right)\right)$ is
MathematicsInverse Trigonometric FunctionsMHT CETMHT CET 2020 (19 Oct Shift 1)
Options:
  • A $\frac{5 \pi}{6}$
  • B $\frac{\pi}{3}$
  • C $\frac{7 \pi}{6}$
  • D $\frac{\pi}{6}$
Solution:
2011 Upvotes Verified Answer
The correct answer is: $\frac{5 \pi}{6}$
Let $\alpha$ and $\beta$ are roots of quadratic equation Given, $\frac{\alpha+\beta}{2}=34$ $\alpha+\beta=68$
and $\sqrt{\alpha \beta}=16$ $\alpha \beta=256$
$\therefore$ Required quadratic equation is, $x^{2}-(\alpha+\beta) x+\alpha \beta=0$ $x^{2}-68 x+256=0$

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