User:PCMorphy72/math

Formula without apparent conditional construct: $$\operatorname {atan2} (y,x)=\lim _{z\to x^{+}}\arctan \left({\frac {y}{z}}\right)+{\frac {\pi }{2}}\operatorname {sgn}(y)\operatorname {sgn}(x)\left(\operatorname {sgn}(x)-1\right)$$

, that is useful e.g. to define the multivalued version of each inverse trigonometric function: e.g. $\tan ^{-1}(x)=\{\arctan(x)+\pi k\mid k\in \mathbb {Z} \}$. However,