HP C/iX Library Reference Manual (30026-90004)

104 Chapter5
HP C/iX Library Function Descriptions
acos
acos
Returns the arc cosine in radians of the input value.
Syntax
#include <math.h>
double acos (double x );
Parameters
x A real number.
Return Values
n The arc cosine of x .
0 The magnitude of the argument of acos is greater than one or less than
negative one. In addition, errno is set to EDOM.
Description
The acos function returns the arc cosine of x , in the range of zero to pi. A message
indicating a DOMAIN error is printed on the standard error output if
x is greater than one or
less than negative one.
Error-handling can be changed by a user-written matherr function.
See Also
matherr(), ANSI C 4.5.2.1, POSIX.1 8.1