###### (This is the documentation for SDL3, which is the current stable version. SDL2 was the previous version!)

# SDL_atan2

Compute the arc tangent of `y / x`

, using the signs of x and y to adjust the result's quadrant.

Defined in <SDL3/SDL_stdinc.h>

## Syntax

`double SDL_atan2(double y, double x);`

## Function Parameters

double |
**y** |
floating point value of the numerator (y coordinate). |

double |
**x** |
floating point value of the denominator (x coordinate). |

## Return Value

(double) Returns arc tangent of of `y / x`

in radians, or, if `x = 0`

, either `-Pi/2`

, `0`

, or `Pi/2`

, depending on the value of `y`

.

The definition of `z = atan2(x, y)`

is `y = x tan(z)`

, where the quadrant of z is determined based on the signs of x and y.

Domain: `-INF <= x <= INF`

, `-INF <= y <= INF`

Range: `-Pi/2 <= y <= Pi/2`

This function operates on double-precision floating point values, use SDL_atan2f for single-precision floats.

To calculate the arc tangent of a single value, use SDL_atan.

This function may use a different approximation across different versions, platforms and configurations. i.e, it can return a different value given the same input on different machines or operating systems, or if SDL is updated.

## Thread Safety

It is safe to call this function from any thread.

## Version

This function is available since SDL 3.1.3.

## See Also

CategoryAPI, CategoryAPIFunction, CategoryStdinc