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.
STANDARDS CONFORMANCE
atan()
: SVID3, XPG4.2, ANSI C, ISO/IEC C99
(including Annex F, ``IEC 60559 floating-point arithmetic'')
atanf(),
atanl()
: ISO/IEC C99 (including Annex F, ``IEC 60559 floating-point arithmetic'')
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