ATAN2 3CW "09 March 2006" "mathcw-1.00"

Table of contents


NAME

atan2f, atan2, atan2l, atan2w, atan2q, atan2ll, atan2df, atan2d, atan2dl, atan2dll - arc tangent function

SYNOPSIS

cc [ flags ] -I/usr/local/include file(s) -L/usr/local/lib -lmcw [ ... ]

#include <mathcw.h>

extern float atan2f (float y, float x);

extern double atan2 (double y, double x);

extern long double atan2l (long double y, long double x);

extern __float80 atan2w (__float80 y, __float80 x);

extern __float128 atan2q (__float128 y, __float128 x);

extern long_long_double atan2ll (long_long_double y, long_long_double x);

extern decimal_float atan2df (decimal_float y, decimal_float x);

extern decimal_double atan2d (decimal_double y, decimal_double x);

extern decimal_long_double atan2dl (decimal_long_double y, decimal_long_double x);

extern decimal_long_long_double atan2dll (decimal_long_long_double y, decimal_long_long_double x);

NB: Functions with prototypes containing underscores in type names may be available only with certain extended compilers.


DESCRIPTION

Compute the principal value of the arc tangent function, using the signs of both arguments to determine the quadrant of the return value. The value of y / x should be in the range [-Infinity,+Infinity], for which the function range is [-pi,+pi].

Special cases for negative zero are:

atan2(+0,pos) = +0
atan2(-0,pos) = -0
atan2(+0,neg) = +pi
atan2(-0,neg) = -pi
These also apply when the second argument is zero.

RETURN VALUES

For in-range arguments, the returned value is in the range [-pi, +pi]. Otherwise, the returned value is a quiet NaN.

ERRORS

For NaN arguments, the returned value is a quiet NaN, and errno is set to EDOM.

SEE ALSO

acos(3CW), asin(3CW), atan(3CW), cos(3CW), cotan(3CW), sin(3CW), tan(3CW).