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JEE Mains · Maths · STD 11 - Trigonometrical equations

સમીકરણ \(\sin ^{7} x+\cos ^{7}=1, x \in[0,4 \pi]\) ના ઉકેલની સંખ્યા મેળવો.

  1. A \(5\)
  2. B \(9\)
  3. C \(11\)
  4. D \(7\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(5\)

Step-by-step Solution

Detailed explanation

\(\sin ^{7} x \leq \sin ^{2} x \leq 1....(1)\) \(\text { and } \cos ^{7} x \leq \cos ^{2} x \leq 1....(2)\) \(\text { also } \sin ^{2} x+\cos ^{2} x=1\) \(\Rightarrow \text { equality must hold for }(1) \,\,(2)\) \(\Rightarrow \sin ^{7} x=\sin ^{2} x \,\, \cos ^{7}=\cos ^{2} x\)…
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