---
name: "fixacos"
section: "3alleg"
platform: "linux"
package: "liballegro-doc"
version: "2:4.2.2-2.2"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/fixacos"
---

# fixacos(3alleg)

Fixed point inverse cosine lookup table. Allegro game programming library.

## NAME

fixacos - Fixed point inverse cosine lookup table. Allegro game programming library.

## SYNOPSIS

**#include \<allegro.h\>**

**fixed fixacos(fixed x);**

## DESCRIPTION

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

```
   fixed result;
   /* Sets `result' to binary angle 128. */
   result = fixacos(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'.

## SEE ALSO