NAME
acos(), acosf(), acosl(), acosw(), acosq() — arccosine functions
SYNOPSIS
#include <math.h>
double acos(double x);
float acosf(float x);
Itanium(R)-based System Only
long double acosl(long double x);
extended acosw(extended x);
quad acosq(quad 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.
Itanium-based System Only
acosl()
is a
long double
version of
acos();
it takes a
long double
argument and returns a
long double
result.
acosw()
is an
extended
version of
acos();
it takes an
extended
argument and returns an
extended
result.
acosq()
is equivalent to
acosl()
on HPUX systems.
USAGE
To use these functions compile either with the default
-Ae
option or with the
-Aa
and the
-D_HPUX_SOURCE
options.
To use (for Itanium-based systems)
acosw()
or
acosq(),
compile also with the
-fpwidetypes
option.
To use any of 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.
For more information, see the
HP-UX Floating-Point Guide.
PA-RISC System Only
Millicode versions of the
acos()
and
acosf()
functions 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.
For special cases, the millicode versions return the values described
in the
RETURN VALUE
section, but do not set
errno.
RETURN VALUE
acos()
returns +0.
If the magnitude of
x
is greater than one,
acos()
returns NaN and raises the invalid exception.
If
x
is NaN,
acos()
returns NaN.
When it raises no other exception,
whether
acos()
raises the
inexact exception is unspecified.
ERRORS
If the magnitude of
x
is greater than one,
acos()
sets
errno
to [EDOM].
Itanium-based System Only
HPUX libm functions on Itanium-based system do not set
errno
by default. For
errno
setting, compile with the
+Olibmerrno
option.
STANDARDS CONFORMANCE
acos()
: SVID3, XPG4.2, ANSI C, ISO/IEC C99
(including Annex F, ``IEC 60559 floating-point arithmetic'')
acosf(),
acosl()
: ISO/IEC C99 (including Annex F, ``IEC 60559 floating-point arithmetic'')
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