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| 1. |
Cot\'4A-1=COSEC\'4A-2cosec2A |
| Answer» cosec^4A - 2cosec^2A =cosec^2A( cosec^2A - 2 ) =cosec^2A( cosec^2A - 1 - 1 ). =cosec^2A( cot^2A - 1 ) =( cot^2A + 1 )( cot^2A - 1)=cot^4A - 1 | |