Answer :
sec x = 1/cos x
cos 2x = cos^2 x - sin^2 x
sec 2x = 1/(cos^2 x - sin^2 x)
Option A is the correct answer.
cos 2x = cos^2 x - sin^2 x
sec 2x = 1/(cos^2 x - sin^2 x)
Option A is the correct answer.