Inverse tangent
= Inverse tangent
{title2=$\arctan$}
= Arctangent
{synonym}
The inverse of the <tangent> restricted to $(-\pi/2,\pi/2)$, taking real values in that interval. Its <derivative> is $(1+x^2)^{-1}$. A formula involving an inverse tangent of a ratio may need a continuous <branch of a multivalued function> to describe a smooth field through a pole of that ratio.