# atan

Return the arc-tangent of the parameters.

## Declaration

 genType atan( genType y, genType x );
 genType atan( genType y_over_x );

## Parameters

 y - Specify the numerator of the fraction whose arctangent to return. x - Specify the denominator of the fraction whose arctangent to return. y_over_x - Specify the fraction whose arctangent to return.

## Description

atan returns either the angle whose trigonometric arctangent is $y \over x$ or y_over_x , depending on which overload is invoked. In the first overload, the signs of $y$ and $x$ are used to determine the quadrant that the angle lies in. The value returned by atan in this case is in the range $[-\pi,\pi]$. The result is undefined if $x = 0$.

For the second overload, atan returns the angle whose tangent is y_over_x . The value returned in this case is in the range $[-{\pi \over 2 },{\pi \over 2}]$.

## Version Support

 atan 1.1+