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

Table of contents


NAME

acospif, acospi, acospil, acospiw, acospiq, acospill, acospidf, acospid, acospidl, acospidll - arc cosine function

SYNOPSIS

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

#include <mathcw.h>

extern float acospif (float x);

extern double acospi (double x);

extern long double acospil (long double x);

extern __float80 acospiw (__float80 x);

extern __float128 acospiq (__float128 x);

extern long_long_double acospill (long_long_double x);

extern decimal_float acospidf (decimal_float x);

extern decimal_double acospid (decimal_double x);

extern decimal_long_double acospidl (decimal_long_double x);

extern decimal_long_long_double acospidll (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 cosine function, defined by acospi(x) = acos(x) / pi.

The inverse function cospi(x) = cos(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 [-1,+1].


RETURN VALUES

For in-range arguments, the returned value is in the range [+0,+pi]. 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

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