Question

which of the following is an identity tan^2x+cos^2x=1, sin^2x cot^2x + cos^2 tan^2x = 1, sinx - cosx +1 = tanx, (1-2sin^2x)csc^x = 4cos^x-2

Answer 1

The first one isnt  because sin^2 x + cos^2 x = 1

the second one is an identity because it simplifies to sin^2 x + cos^2 x = 1