Question

The value of 7 cot2 A - 7 cosec2A is =

1) 7 2) -7

3)1/2 4) none of these

Answer 1

We know cot^2A + 1 = cosec^2A

Thus cot^2A - cosec^2A = -1

or 7cot^2A - 7cosec^2A = -7

Answer 2

cot²A-cosec²A=-1
∴7cot²A-7cosec²A=7(cot²A-cosec²A)
                             =7×-1
                             =-7
so,option 2 is correct.
hope it helps you.