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