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TS EAMCET · Maths · Trigonometric Ratios & Identities

If x+1x=2cosθ, then x6+x-6=

  1. A 2cos6θ
  2. B 2cos12θ
  3. C 2cos3θ
  4. D 2sin3θ
Verified Solution

Answer & Solution

Correct Answer

(B) 2cos12θ

Step-by-step Solution

Detailed explanation

Given that x+1x=2cosθ square on both the sides x+1x+2=4cos2θ x+1x=22cos2θ-1=2cos2θ cube on both the sides x+1x3=8cos32θ x3+1x3+3x+1x=8cos32θ x3+1x3=8cos32θ-2cos2θ ⇒x3+1x3=2cos2θ4cos22θ-1…
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