ATANPI 3CW "21 March 2008" "mathcw-1.00"

Table of contents


NAME

atanpif, atanpi, atanpil, atanpiw, atanpiq, atanpill, atanpidf, atanpid, atanpidl, atanpidll - arc tangent function

SYNOPSIS

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

#include <mathcw.h>

extern float atanpif (float x);

extern double atanpi (double x);

extern long double atanpil (long double x);

extern __float80 atanpiw (__float80 x);

extern __float128 atanpiq (__float128 x);

extern long_long_double atanpill (long_long_double x);

extern decimal_float atanpidf (decimal_float x);

extern decimal_double atanpid (decimal_double x);

extern decimal_long_double atanpidl (decimal_long_double x);

extern decimal_long_long_double atanpidll (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, defined by atanpi(x) = atan(x) / pi.

The inverse function tanpi(x) = tan(pi * x), avoid range-reduction issues because the argument x is always an exact scaling of pi.

The value of x should be in the range [-Infinity,+Infinity].


RETURN VALUES

For in-range arguments, the returned value is in the range [-pi/2, +pi/2]. Otherwise, the returned value is a quiet NaN.

ERRORS

For out-of-range, Infinity and NaN arguments, the returned value is a quiet NaN, and errno is set to EDOM.

SEE ALSO

acospi(3CW), asinpi(3CW), atan2pi(3CW), cospi(3CW), cotanpi(3CW), sinpi(3CW), tanpi(3CW).