Specify the fraction whose arctangent to return.

.RE

.SH "DESCRIPTION"

.PP 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 $x = 0$.

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

.SH "VERSION SUPPORT"

.TS allbox tab(:); lB cB s s s s s s s s s s s lB cB cB cB cB cB cB cB cB cB cB cB cB. T{

T}:T{ OpenGL Shading Language Version T} T{ Function Name T}:T{ 1.10 T}:T{ 1.20 T}:T{ 1.30 T}:T{ 1.40 T}:T{ 1.50 T}:T{ 3.30 T}:T{ 4.00 T}:T{ 4.10 T}:T{ 4.20 T}:T{ 4.30 T}:T{ 4.40 T}:T{ 4.50 T} l c c c c c c c c c c c c. T{ atan T}:T{ ✔ T}:T{ ✔ T}:T{ ✔ T}:T{ ✔ T}:T{ ✔ T}:T{ ✔ T}:T{ ✔ T}:T{ ✔ T}:T{ ✔ T}:T{ ✔ T}:T{ ✔ T}:T{ ✔ T}

.SH "SEE ALSO"

.PP sin(), cos(), tan()

.SH "COPYRIGHT"

.PP Copyright © 2011-2014 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. https://opencontent.org/openpub/.