Calculate ddxtan−1(xa)\frac{d}{dx} \tan^{-1}(\frac{x}{a})dxdtan−1(ax).
aa2+x2\frac{a}{a^2 + x^2}a2+x2a
1a2+x2\frac{1}{a^2 + x^2}a2+x21
xa2+x2\frac{x}{a^2 + x^2}a2+x2x
a2a2+x2\frac{a^2}{a^2 + x^2}a2+x2a2