acos
arc cosine function
You're viewing an older version of this page (#3334). View the current version.
NAME
acos
INTERFACE
#include <math.h> double acos (double x) long acosl (long double x) float acosf (float x)
DESCRIPTION
The acos function computes the principal value of the arc cosine of x in the range [0, ].
acosl is a long double verion; it takes a long double argument and returns a long double result.
The arc cosine is the inverse cosine, usually donated as . It is a multi valued functions of the following form:
Example 1
#include <stdio.h>
#include <math.h>
int main(void)
{
double result, x=0.5;
result = acos(x);
printf("The arc cosine of %lf is %lf\n", x, result);
return 0;
}output
The arc cosine of 0.500000 is 1.047198SPECIAL VALUES
acos ( 1 ) returns +0.
acos ( x ) returns a NAN and raises the invalid floating-point exception for |x| > 1.
SEE ALSO
sin, cos , tan, asin, atan , atan2, sinh , cosh , tanh
STANDARDS
The acos function conforms to ISO/IEC 9899:1999(E).