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If 2cos2 θ – 11 cos θ + 5 = 0, then find the possible values of cos θ. |
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Answer» 2cos2 θ – 11 cos θ + 5 = 0 ∴ 2cos2 θ – 10 cos θ – cos θ + 5 = 0 ∴ 2cos θ(cos θ – 5) – 1 (cos θ – 5) = 0 ∴ (cos θ – 5) (2cos θ – 1) = 0 cos θ – 5 = 0 or 2cos θ – 1 = 0 ∴ cos θ = 5 or cos θ = 1/2 Since, -1 ≤ cos θ ≤ 1 ∴ cos θ = 1/2 |
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