AP EAMCET · Maths · Trigonometric Ratios & Identities
\(\cos ^3 \frac{\pi}{8} \cos \frac{3 \pi}{8}+\sin ^3 \frac{\pi}{8} \sin \frac{3 \pi}{8}=\)
- A \(\frac{1}{2 \sqrt{2}}\)
- B \(\frac{1}{2}\)
- C \(\frac{1}{\sqrt{2}}\)
- D \(\frac{1}{4}\)
Answer & Solution
Correct Answer
(A) \(\frac{1}{2 \sqrt{2}}\)
Step-by-step Solution
Detailed explanation
\( = \frac{1}{4}(\cos \frac{3 \pi}{8} + 3 \cos \frac{\pi}{8}) \cos \frac{3 \pi}{8} + \frac{1}{4}(3 \sin \frac{\pi}{8} - \sin \frac{3 \pi}{8}) \sin \frac{3 \pi}{8} \)…
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