HP-UX Reference (11i v2 04/09) - 3 Library Functions A-M (vol 6)

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acos(3M) acos(3M)

NAME

acos(), acosf(), acosl(), acosw(), acosq() - arccosine functions

SYNOPSIS

#include <math.h>

double acos(double x);

float acosf(float x);

Itanium-based Systems 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 Pi.

acosf() is a float version of acos()

; it takes a float argument and returns a float result.

Itanium-based Systems 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

acosw() or acosq() (on Itanium-based systems), 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 Systems 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 ver-

sions, 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 Systems Only

HPUX libm functions on Itanium-based systems do not set

errno by default. For errno setting, com-

pile with the +Olibmerrno option.