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If sinx = 2/3, then find the value of cos3x.1. -0.57972. 0.56783. 0.67354. -0.8765 |
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Answer» Correct Answer - Option 1 : -0.5797 Given- sinx = 2/3 Formula Used- cosx = √(1 - sin2x) cos3x = 4cos3x - 3cosx Calculation - cosx = √(1 - 4/9) ⇒ √(5/9) ⇒ √5/3 cos3x = 4 × (√5/3)3 - 3 × √5/3 ⇒ cos3x = 20√5/27 - √5 ⇒ cos3x = -7√5/27 ∴ cos3x = -0.5797 |
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