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JEE Mains · Maths · STD 11 - Trigonometrical equations

\(2\,{\sin ^3}\,\alpha  - 7\,{\sin ^2}\,\alpha  + 7\,\sin \,\alpha  = 2\) ના સમાધાન માટે \(\alpha \)ની કિંમત \([0, 2\pi]\) માં કેટલી મળે ?

  1. A \(6\)
  2. B \(4\)
  3. C \(3\)
  4. D \(1\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(3\)

Step-by-step Solution

Detailed explanation

\(2 \sin ^{3} \alpha-7 \sin ^{2} \alpha+7 \sin \alpha-2=0\) \(\Rightarrow 2 \sin ^{2} \alpha(\sin \alpha-1)-5 \sin \alpha\) \((\sin \alpha-1)+2(\sin \alpha-1)=0\) \(\Rightarrow(\sin \alpha-1)\left(2 \sin ^{2} \alpha-5 \sin \alpha+2\right)\) \(=0\) \(\Rightarrow \sin \alpha-1=0\)…
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