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If cot-1 (√sin α) + tan-1 (√sin α) = u, then cos 2u is equal to ...(a) tan2 α(b) 0(c) -1 (d) tan 2α |
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Answer» (c) -1 cot-1 x + tan-1 x = π/2 ⇒ u = π/2 so 2u = π ∴ cos 2u = cos π = -1 |
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