# atan

## Name

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 the angle whose trigonometric arctangent is $y x$ 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 values returned by atan in this case are in the range $− π π$. Results are undefined if $x$ is zero.

For the second overload, atan returns the angle whose tangent is $y_over_x$. Values returned in this case are in the range $− π 2 π 2$.

## Version Support

OpenGL Shading Language Version
Function Name 1.10 1.20 1.30 1.40 1.50 3.30 4.00 4.10 4.20 4.30 4.40 4.50
atan