---
name: "al_fixacos"
section: "3"
platform: "linux"
package: "allegro"
version: "5.2.11.3-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/al_fixacos"
---

# al\_fixacos(3)

Allegro 5 API

## NAME

al\_fixacos - Allegro 5 API

## SYNOPSIS

-

  ```
  #include <allegro5/allegro.h>
  al_fixed al_fixacos(al_fixed x);
  ```

## DESCRIPTION

This function finds the inverse cosine of a value using a lookup table. The input must be a fixed point value. The inverse cosine is defined only in the domain from -1 to 1. Outside of this input range, the function will set Allegro’s errno to EDOM and return zero.

Example:

-

  ```
  al_fixed result;
  /* Sets result to binary angle 128. */
  result = al_fixacos(al_itofix(-1));
  ```

## RETURN VALUE

Returns the inverse sine of a fixed point value, measured as fixed point binary format angle, or zero if the input was out of range. All return values of this function will be in the range 0 to 128.