1.

Prove that: `cotAcot2A-cot2Acot3A-cot3AcotA=1`

Answer» `3A=2A+A`
`rArr cot3A=cot(2A+A)`
`rArr cot3A=(cot2AcotA-1)/(cotA+cot2A)`
`rArr cot3A cotA+cot2Acot3A=cotAcot2A-1`
`rArr 1= cotAcot2A-cot2Acot3A-cot3AcotA` Hence Proved.


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