HP-UX Reference (11i v1 00/12) - 3 Library Functions A-M (vol 6)

ManualsBrandsHP ManualsSoftwareHP-UX Reference Manuals

__________________________________________________________________________________________________________________________________________________________________________________________________

STANDARD Printed by: Nora Chuang [nchuang] STANDARD

/build/1111/BRICK/man3/!!!intro.3c

________________________________________________________________

___ ___

acos(3M) acos(3M)

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 speci-

fying

-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

acos() fails, errno is set to the following value.

[EDOM] The magnitude of x is greater than one.