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TS EAMCET · Maths · Trigonometric Equations

If 6cos2θ+2cos2θ2+2sin2θ=0, -π<θ<π, then θ=

  1. A π3
  2. B π3, cos-135
  3. C cos-135
  4. D ±π3, ±π-cos-135
Verified Solution

Answer & Solution

Correct Answer

(D) ±π3, ±π-cos-135

Step-by-step Solution

Detailed explanation

Given, θ∈-π,π 6cos2θ+2cos2θ2+2sin2θ=0 ⇒61-2sin2θ+2cos2θ2+2sin2θ=0 ⇒6-10sin2θ+2cos2θ2=0 ⇒6-101-cos2θ+1+cosθ=0 ⇒10cos2θ+cosθ-3=0 ⇒10cos2θ-5cosθ+6cosθ-3=0…