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JEE Mains · Maths · STD 11 - 3. trignometrical ratios,functions and identities

माना कि \( cos(\alpha+\beta)=-\frac{1}{10} \) और \( sin(\alpha-\beta)=\frac{3}{8} \) जहाँ \( 0<\alpha<\frac{\pi}{3} \) और \( 0<\beta<\frac{\pi}{4} \). यदि \( tan~2\alpha=\frac{3(1-r\sqrt{5})}{\sqrt{11}(s+\sqrt{5})}, r, s\in\mathbb{N} \), तो \( r+s \) = ___ है।

  1. A 10
  2. B 15
  3. C 20
  4. D 25
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Answer & Solution

Correct Answer

(C) 20

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Detailed explanation

\(\tan 2 \alpha=\tan [(\alpha+\beta)+(\alpha-\beta)]\) \(\tan 2 \alpha=\frac{\tan (\alpha+\beta)+\tan (\alpha-\beta)}{1-\tan (\alpha+\beta) \cdot \tan (\alpha-\beta)}\)…
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