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

SDL_acos

Compute the arc cosine of x.

Header File

Syntax

double SDL_acos(double x);

Function Parameters

x	floating point value

Return Value

Returns arc cosine of x, in radians

Remarks

The definition of y = acos(x) is x = cos(y).

Domain: -1 <= x <= 1

Range: 0 <= y <= Pi

This function operates on double-precision floating point values, use SDL_acosf for single-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 3.0.0.

Code Examples

/* acos(x) = Pi/2 - asin(x) */
SDL_Log("acos(0):\t\t%f", SDL_acos(0.));
SDL_Log("Pi/2 - asin(0):\t%f", SDL_PI_D / 2 - SDL_asin(0));

/* acos(-x) = Pi  - acos(x) */
SDL_Log("acos(-(-1)):\t%f", SDL_acos(-(-1)));
SDL_Log("Pi - acos(-1):\t%f", SDL_PI_D - SDL_acos(-1));