Which of the following is not an identity?

A. (tanx + cotx)^2 = csc^2 x + sec^2 x
B. (cosx + sinx)^2 = 1 + 2cosx sinx
C. tan^2x = sec^2x - sin^2x - cos^2x
D. 1+cos^2x/sin^2x=1

Question

Which of the following is not an identity?

 		A.	(tanx + cotx)^2 = csc^2 x + sec^2 x
 		B.	(cosx + sinx)^2 = 1 + 2cosx sinx
 		C.	tan^2x = sec^2x - sin^2x - cos^2x
 		D.	1+cos^2x/sin^2x=1

anonymous · Answer

You will have to verify each to see which is not an identity

anonymous · Answer

how do i do that

anonymous · Answer

verification involves you changing one side and trying to make it appear like the second side by manipulating the trig expressions