1.
Let α(0,π/2)\alpha\in(0,\pi/2) be constant. If tanx+tanαtanxtanαdx=A(x)cos2α+B(x)sin2α+C\int \frac{\tan x+\tan\alpha}{\tan x-\tan\alpha}dx = A(x)\cos2\alpha + B(x)\sin2\alpha + C, then A(x),B(x)A(x), B(x) are respectively