HP-UX Reference (11i v3 07/02) - 3 Library Functions A-M (vol 6)

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atan(3M) atan(3M)

NAME

atan( ), atanf(), atanl(), atanw(), atanq() - arctangent functions

SYNOPSIS

#include <math.h>

double atan(double x);

float atanf(float x);

HP Integrity Server Only

long double atanl(long double x);

extended atanw(extended x);

quad atanq(quad x);

DESCRIPTION

atan() returns the arctangent of x, in the range −π/2 to π/2.

atanf() is a float version of atan(); it takes a float argument and returns a float

result.

Integrity Server Only

atanl() is a long double version of atan(); it takes a long double argument and returns a

long double result.

atanw() is an extended version of atan(); it takes an extended argument and returns an

extended result.

atanq() is equivalent to atanl() on HP-UX 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 Integrity servers)

atanw() or atanq(), compile also with -fpwidetypes .

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 for HP Integrity servers at the following site:

http://www.hp.com/go/fp

PA-RISC Only

Millicode versions of the

atan() and atanf() 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 same values as their standard library counterparts (see

the RETURN VALUE section).

RETURN VALUE

atan(±0) returns ±0.

If x is ±INFINITY, atan() returns ±π/2 respectively.

If x is NaN, atan() returns NaN.

Whether atan() raises the inexact exception is unspeciﬁed.

ERRORS

No errors are deﬁned.