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31 lines
1.2 KiB
Markdown
31 lines
1.2 KiB
Markdown
## Atan
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Return the arc-tangent of the parameters
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### Declaration
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```glsl
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float atan(float y, float x)
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vec2 atan(vec2 y, vec2 x)
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vec3 atan(vec3 y, vec3 x)
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vec4 atan(vec4 y, vec4 x)
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float atan(float y_over_x)
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vec2 atan(vec2 y_over_x)
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vec3 atan(vec3 y_over_x)
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vec4 atan(vec4 y_over_x)
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```
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### Parameters
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```y``` specify the numerator of the fraction whose arctangent to return.
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```x``` specify the denominator of the fraction whose arctangent to return.
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```y_over_x``` specify the fraction whose arctangent to return.
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### Description
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```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 -PI and PI. Results are undefined if ```x``` is zero.
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For the second overload, ```atan()``` returns the angle whose tangent is ```y_over_x```. Values returned in this case are in the range -PI to PI.
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### See Also
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[cos](index.html#cos.md), [acos](index.html#acos.md), [sin](index.html#sin.md), [asin](index.html#asin.md), [atan](index.html#atan.md), [Chapter 05: Shaping Functions](../05/), [Chapter 06: Color](../06/)
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