Don L. answered 06/17/19
Fifteen years teaching and tutoring basic math skills and algebra
Hi Ac, tan2 x = sec2 x - 1 (identity.) Replacing the tan2 x with sec2 x - 1 gives:
sec2 x -1 + sec x - 1
--------------------------
sec x - 1
Rearranging the numerator:
sec2 x + sec x - 2
------------------------
sec x - 1
Factor the numerator into two binomials:
(sec x + 2) (sec x - 1)
-----------------------------
sec x - 1
The sec x - 1 cancels leaving sec x + 2.
Questions?