newlib/libm/mathfp/s_acos.c

   1
   2 /* @(#)z_acos.c 1.0 98/08/13 */
   3
   4 /*
   5 FUNCTION
   6         <<acos>>, <<acosf>>---arc cosine
   7
   8 INDEX
   9         acos
  10 INDEX
  11         acosf
  12
  13 SYNOPSIS
  14         #include <math.h>
  15         double acos(double <[x]>);
  16         float acosf(float <[x]>);
  17
  18 DESCRIPTION
  19
  20         <<acos>> computes the inverse cosine (arc cosine) of the input value.
  21         Arguments to <<acos>> must be in the range @minus{}1 to 1.
  22
  23         <<acosf>> is identical to <<acos>>, except that it performs
  24         its calculations on <<floats>>.
  25
  26 RETURNS
  27         @ifnottex
  28         <<acos>> and <<acosf>> return values in radians, in the range of 0 to pi
  29 .
  30         @end ifnottex
  31         @tex
  32         <<acos>> and <<acosf>> return values in radians, in the range of <<0>> t
  33 o $\pi$.
  34         @end tex
  35
  36         If <[x]> is not between @minus{}1 and 1, the returned value is NaN
  37         (not a number) the global variable <<errno>> is set to <<EDOM>>, and a
  38         <<DOMAIN error>> message is sent as standard error output.
  39
  40 QUICKREF
  41  ansi posix rentrant
  42  acos    y,y,m
  43  acosf   n,n,m
  44
  45 MATHREF
  46  acos, [-1,1], acos(arg),,,
  47  acos, NAN,    arg,DOMAIN,EDOM
  48
  49 MATHREF
  50  acosf, [-1,1], acosf(arg),,,
  51  acosf, NAN,    argf,DOMAIN,EDOM
  52
  53 */
  54
  55 /*****************************************************************
  56  * Arccosine
  57  *
  58  * Input:
  59  *   x - floating point value
  60  *
  61  * Output:
  62  *   arccosine of x
  63  *
  64  * Description:
  65  *   This routine returns the arccosine of x.
  66  *
  67  *****************************************************************/
  68
  69 #include "fdlibm.h"
  70 #include "zmath.h"
  71
  72 #ifndef _DOUBLE_IS_32BITS
  73
  74 double
  75 acos (double x)
  76 {
  77   return (asine (x, 1));
  78 }
  79
  80 #endif /* _DOUBLE_IS_32BITS */