MHT CET · Maths · Trigonometric Ratios & Identities
\(\cos ^4 \frac{\pi}{8}+\cos ^4 \frac{3 \pi}{8}+\cos ^4 \frac{5 \pi}{8}+\cos ^4 \frac{7 \pi}{8}=\)
- A \(\frac{1}{2}\)
- B \(\frac{3}{2}\)
- C \(\frac{1}{4}\)
- D \(\frac{3}{4}\)
Answer & Solution
Correct Answer
(B) \(\frac{3}{2}\)
Step-by-step Solution
Detailed explanation
\( \cos ^4 \frac{\pi}{8}+\cos ^4 \frac{3 \pi}{8}+\cos ^4 \frac{5 \pi}{8}+\cos ^4 \frac{7 \pi}{8} = 2 \left( \cos ^4 \frac{\pi}{8}+\cos ^4 \frac{3 \pi}{8} \right) \)
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