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(This is the documentation for SDL3, which is under heavy development and the API is changing! SDL2 is the current stable version!)


Compute the arc tangent of y / x, using the signs of x and y to adjust the result's quadrant.

Header File

Defined in <SDL3/SDL_stdinc.h>


float SDL_atan2f(float y, float x);

Function Parameters

float y floating point value of the numerator (y coordinate).
float x floating point value of the denominator (x coordinate).

Return Value

(float) 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 single-precision floating point values, use SDL_atan2 for double-precision floats.

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

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.


This function is available since SDL 3.0.0.

See Also

CategoryAPI, CategoryAPIFunction, CategoryStdinc

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