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# docs.GL

GLSL 4
GLSL ES 3

# 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 ES Shading Language Version
--- | ---
Function Name | 1.00 | 3.00 | 3.10
atan | ✔ | ✔ | ✔

## See Also

sin, cos, tan, asin, acos

## Copyright

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/.

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