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AP EAMCET · Maths · Trigonometric Ratios & Identities

\(\cos ^2\left(\frac{7 \pi}{8}\right)+\cos ^2\left(\frac{5 \pi}{8}\right)+\cos ^2\left(\frac{3 \pi}{8}\right)+\cos ^2\left(\frac{\pi}{8}\right)=\)

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

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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