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AP EAMCET · Maths · Trigonometric Equations

If \(f_n(x)=\frac{1}{2 n}\left[\sin ^{2 n} x+\cos ^{2 n} x\right]\), then \(f_1(x)+f_2(x)-f_3\) (x) \(=\)

  1. A 0
  2. B \(\frac{5}{12}\)
  3. C \(\frac{11}{12}\)
  4. D \(\frac{7}{12}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\frac{7}{12}\)

Step-by-step Solution

Detailed explanation

\begin{aligned} & \text {} f_n(x)=\frac{1}{2 n}\left[\sin ^{2 n} x+\cos ^{2 n} x\right] \\ & f_1(x)+f_2(x)+f_3(x) \\ & =\frac{1}{2}\left[\sin ^2 x+\cos ^2 x\right]+\frac{1}{4}\left[\sin ^4 x+\cos ^4 x\right]-\frac{1}{6}\left[\sin ^6 x+\cos ^6 x\right] \\ & =\frac{1}{2} \times…