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.
Otherwise, the compiler will not find a correct declaration of
acosf(),
and error messages or incorrect results will occur.
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, link in the math library by specifying
-lm
on the compiler or linker command line.
Millicode versions of the
acos()
function are available in the library
/usr/lib/milli.a.
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
+DA1.1
option (the default on PA1.1-based systems) or the
+DA2.0
option (the default on PA2.0-based systems) and 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 zero 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
Printable version
