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cot(theta)^4 - 1=cosec^4*theta - 2*cosec^2*theta |
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Answer» Let theta = A LHS = cot^4A-1 = (cot^2A)^2 - 1^2 = (cot^2A + 1)(cot^2A - 1) = cosec^2A(cosec^2A - 1 - 1) [since 1+cot^2A = cosec^2A which implies cot^2A = cosec^2A-1] = cosec^2A(cosec^2A - 2) = cosec^4A - 2cosec^2A = RHS Hence proved |
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