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atan.3m (2010 09)

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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 ver-
sions, 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.
SEE ALSO
acos(3M), asin(3M), atand(3M), atan2(3M), catan(3M), cos(3M), sin(3M), tan(3M), math(5).
STANDARDS CONFORMANCE
atan() : SVID3, XPG4.2, ANSI C, ISO/IEC C99 (including Annex F, ‘‘IEC 60559 floating-point arith-
metic’’)
atanf(), atanl() : ISO/IEC C99 (including Annex F, ‘‘IEC 60559 floating-point arithmetic’’)
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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