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

# SDL_acosf

Compute the arc cosine of `x`

.

Defined in <SDL3/SDL_stdinc.h>

## Syntax

`float SDL_acosf(float x);`

## Function Parameters

float |
**x** |
floating point value. |

## Return Value

(float) Returns arc cosine of `x`

, in radians.

The definition of `y = acos(x)`

is `x = cos(y)`

.

Domain: `-1 <= x <= 1`

Range: `0 <= y <= Pi`

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

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