TS EAMCET · Maths · Trigonometric Equations
\(\cos ^4 \frac{\pi}{8}+\cos ^4 \frac{2 \pi}{8}+\cos ^4 \frac{3 \pi}{8}+\cos ^4 \frac{4 \pi}{8}+\cos ^4 \frac{5 \pi}{8}\) \(+\cos ^4 \frac{6 \pi}{8}+\cos ^4 \frac{7 \pi}{8}+\cos ^4 \frac{8 \pi}{8}\) is equal to
- A 3
- B -1
- C 1
- D 4
Answer & Solution
Correct Answer
(A) 3
Step-by-step Solution
Detailed explanation
\begin{aligned} & \cos ^4 \frac{\pi}{8}+\cos ^4 \frac{2 \pi}{8}+\cos ^4 \frac{3 \pi}{8}+\cos ^4 \frac{4 \pi}{8} \\ & +\cos ^4 \frac{5 \pi}{8}+\cos ^4 \frac{6 \pi}{8}+\cos ^4 \frac{7 \pi}{8}+\cos ^4 \frac{8 \pi}{8} \\ & =\left(\cos ^4 \frac{\pi}{8}+\cos \frac{7…
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