ACOS(3) | Library Functions Manual | ACOS(3)

# NAME

`acos`, `acosf`, `acosl` — arc cosine functions

# SYNOPSIS

Math Library (libm, -lm)
`#include <math.h>`

double
`acos`(double x);

float
`acosf`(float x);

long double
`acosl`(long double x);

# DESCRIPTION

The `acos`() function computes the principal value of the arc cosine of x in the range [0, pi]. The `acosf`() function is a single precision version of `acos`(). The `acosl`() function is an extended precision version of `acos`().

# RETURN VALUES

If |x|>1, `acos`(x), `acosf`(x) and `acosl`(x) set the global variable errno to `EDOM`.

# SEE ALSO

asin(3), atan(3), atan2(3), cos(3), cosh(3), sin(3), sinh(3), tan(3), tanh(3)

June 7, 2025 | Debian