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JEE Mains · Maths · STD 12 - 6. Application of derivatives

If \(\theta_{1}\) and \(\theta_{2}\) be respectively the smallest and the largest values of \(\theta\) in \((0,2 \pi)-\{\pi\}\) which satisfy the equation, \(\quad 2 \cot ^{2} \theta-\frac{5}{\sin \theta}+4=0,\) then \(\int\limits_{\theta_{1}}^{\theta_{2}} \cos ^{2} 3 \theta \mathrm{d} \theta \) is equal to

  1. A \(\frac{2\pi}{3}\)
  2. B \(\frac{\pi}{3}+\frac{1}{6}\)
  3. C \(\frac{\pi}{9}\)
  4. D \(\frac{\pi}{3}\)
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Answer & Solution

Correct Answer

(D) \(\frac{\pi}{3}\)

Step-by-step Solution

Detailed explanation

\(2 \cos ^{2} \theta-5 \sin \theta+4 \sin ^{2} \theta=0\) \(3 \sin ^{2} \theta-5 \sin \theta+2=0\) \(\sin \theta=\frac{1}{2}, 2(\text { Rejected })\)…
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