acos(3) - Linux man page

Name

acos, acosf, acosl - arc cosine function

Synopsis

#include <math.h>
double acos(double x);float acosf(float x);long double acosl(long double
x);

Link with -lm.

Description

The acos() function calculates the arc cosine of x; that is the value whose cosine is x. If x falls outside the range -1 to 1, acos() fails and errno is set.

Return Value

The acos() function returns the arc cosine in radians and the value is mathematically defined to be between 0 and PI (inclusive).

Errors

EDOM: x is out of range.

Conforming to

SVr4, POSIX.1-2001, 4.3BSD, C89. The float and long double variants are C99 requirements.