In Exercises 11-16, verify the identity.
11. 2 sec² x - sec² x sin² x - sin² x - cos² x = 1
12.
1 + sec(-x)
sin(-x)+tan(-x)
= -CSC X
13. 2+ cos² x - 3 cos4 x = sin² x(2 + 3 cos x)
tan³ x-1
14.
= tan² x + tan x + 1
tan x-1
15.
COS X
= sec x + tan x
1 - sin x
16. sec² x + csc² x = csc² x sec² x