Question

Which of the following is an identity?

A. csc^2 x + cot^2 x = 1
B. (cscx + cotx)^2 = 1
C. sec^2 x sec^2 x + 1 = tan^2 x csc^2 x
D. sin^2 x - cos^2 x = 1

Answer 1

I am not sure at all but I think the answer is C.

Answer 2

there is an identity  csc^2 x = 1 + cot^2x  so it cant be A

Nor D  because sin^2 x + cos^2 x = 1

I think Its C 

converting to sin's and cos's 

1 / cos^4 x  + 1    =   sin^2 x / cos^2x  *   1 / sin^2 x   = 1 / cos^2 x

I dont think any are identities
You sure you have  the question correct?