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MHT CET · Maths · Trigonometric Ratios & Identities

\(\sqrt{2+\sqrt{2+2 \cos 4 \theta}}=\)

  1. A \(2 \cos \theta\)
  2. B \(\frac{\cos \theta}{2}\)
  3. C \(\frac{\cos \theta}{\sqrt{2}}\)
  4. D \(\sqrt{2} \cdot \cos \theta\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(2 \cos \theta\)

Step-by-step Solution

Detailed explanation

\(\sqrt{2+\sqrt{2+2 \cos 4 \theta}} =\sqrt{2+\sqrt{2(1+\cos 4 \theta)}} \)
\( =\sqrt{2+\sqrt{2 \times 2 \cos ^{2} 2 \theta}}=\sqrt{2+2 \cos ^{2} 2 \theta} \)
\( =\sqrt{2\left(1+\cos ^{2} 2 \theta\right)}=\sqrt{2 \times 2 \cos ^{2} \theta}=2 \cos \theta\)