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If sin A = \(\frac{1}{2}\) then 4 cos3 A – 3 cos A is: (a) 1 (b) 0 (c) \(\frac{\sqrt{3}}{2}\)(d) \(\frac{1}{\sqrt{2}}\) |
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Answer» (b) 0 Given sin A = \(\frac{1}{2}\) sin A = sin 30° ∴ A = 30° [∵ 4 cos3 A – 3 cos A = cos 3A] = cos(3 x 30°) = cos 90° = 0 |
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