\(sin(2x) = 2 sin x cos x \\ \\ cos(2x) = cos^2 x - sin^2 x\)
After Substituting:
\(\frac{2 sin x cos x}{1+cos^2 x - sin^2 x}\)
Use pythagorean thm:
\(1 - sin^2 x = cos^2 x\)
......................
\(\frac{2 sin x cos x}{2cos^2 x} \\ \\ = \frac{sinx }{cos x} \\ \\ = tan x\)
