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If 3 tan2 - 1 = 0, find cos 20, given that is acute. |
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Answer» n :- LET theta = A 3tan²A - 1 = 0 3tan²A = 1 tan²A = 1/3 tan A = √(1/3) tan A = 1/√3 tan A = tan 30 A = 30 Now, COS 2A = Cos ( 2 × 30) = Cos 60 = 1/2Cos²A = Cos ² 30 = (√3/2)² = 3/4 |
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