Solving an Integral without Symmetry: A Challenge

[SeReNiTy]

I'm trying to solve a special integral.

$$\int{\frac{1}{1+[Tan(x)]^a}}dx$$

So far I've tried constructing a function F(a) and differentitating to show that it is a 0, hence any a would result in the same answer. Thus chose a = 2, and solve it quite easily. Although, all my arguments rely on symmetry, just wondering if it is possible to solve without symmetry.

 

[SeReNiTy]

don't worry guys, I've worked it out