prove that left side is equal to right side:
sec^2x-csc^2x=(tan^2x + 1)-(1 +cot^2x
=tan^2 x + 1-1 - cot^2 x
=tan^2x - cot^2x
=(tan x - cotx)(tan x + cotx)..................use identities tanx= sinx/cosx and cotx = cosx/sinx
=(tan x - cotx)(sin x/cos x +cos x/sin x)
=(tan x - cotx)((sin xsin x +cos xcos x)/sin xcos x
=(tan x - cotx)((sin ^2x +cos^2 x)/sin xcos x
=
=