1+cos2A= 2/1+tan^(2)A

I don't understand what are you actually looking for, the expression you wrote looks like an identity to me. May be you want to prove that this is correct. Here is a prove :

1 + cos(2A) = 2 cos²(A) = 2 / sec²(A) = 2 / [ 1 + tan²(A) ]