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?
