Fuente TeX:

  A(D) = - \frac{\pi}{2} + \frac{6}{\sqrt{3}}  \int_{\sqrt{3} \tan(0)} ^{ \sqrt{3} \tan(\frac{\pi}{4}) } \frac{1}{1+x^2} du = - \frac{\pi}{2} + \frac{6}{\sqrt{3}} \arctan{x} \big|_0 ^{ \sqrt{3} } = - \frac{\pi}{2} + 2\sqrt{3} \big(  \arctan{\sqrt{3}} - \arctan{0} \big)