NAME
acos(), acosf() — arccosine functions
SYNOPSIS
#include <math.h>
double acos(double x);
float acosf(float x);
DESCRIPTION
acos()
returns the arccosine of
x
in the range 0 to π.
acosf()
is a
float
version of
acos();
it takes a
float
argument and returns a
float
result. To use this function, compile either with the default
-Ae
option or with the
-Aa
and
-D_HPUX_SOURCE
options.
acosf()
is not specified by any standard, but it is named in accordance with
the conventions specified in the "Future Library Directions" section
of the ANSI C standard.
To use these functions, make sure your program includes
<math.h>,
and link in the math library by specifying
-lm
on the compiler or linker command line.
Millicode versions of the
acos()
function are available.
Millicode versions of math library functions are usually faster than
their counterparts in the standard library. To use these versions,
compile your program with the
+Olibcalls
or the
+Oaggressive
optimization option.
If an error occurs, the millicode versions return the value described
in the
RETURN VALUE
section, but do not set
errno.
For more information, see the
HP-UX Floating-Point Guide.
RETURN VALUE
If
x
is NaN,
acos()
returns NaN.
If the magnitude of
x
is greater than one,
acos()
returns NaN and sets
errno
to [EDOM].
ERRORS
If
acos()
fails,
errno
is set to the following value.
- [EDOM]
The magnitude of
x
is greater than one.
STANDARDS CONFORMANCE
acos(): SVID3, XPG4.2, ANSI C
