newlib/libm/mathfp/s_cosh.c

   1
   2 /* @(#)z_cosh.c 1.0 98/08/13 */
   3
   4 /*
   5
   6 FUNCTION
   7         <<cosh>>, <<coshf>>---hyperbolic cosine
   8
   9 SYNOPSIS
  10         #include <math.h>
  11         double cosh(double <[x]>);
  12         float coshf(float <[x]>);
  13
  14 DESCRIPTION
  15
  16         <<cosh>> computes the hyperbolic cosine of the argument <[x]>.
  17         <<cosh(<[x]>)>> is defined as
  18         @ifnottex
  19         . (exp(x) + exp(-x))/2
  20         @end ifnottex
  21         @tex
  22         $${(e^x + e^{-x})} \over 2$$
  23         @end tex
  24
  25         Angles are specified in radians.
  26
  27         <<coshf>> is identical, save that it takes and returns <<float>>.
  28
  29 RETURNS
  30         The computed value is returned.  When the correct value would create
  31         an overflow,  <<cosh>> returns the value <<HUGE_VAL>> with the
  32         appropriate sign, and the global value <<errno>> is set to <<ERANGE>>.
  33
  34 PORTABILITY
  35         <<cosh>> is ANSI.
  36         <<coshf>> is an extension.
  37
  38 QUICKREF
  39         cosh ansi pure
  40         coshf - pure
  41 */
  42
  43 /******************************************************************
  44  * Hyperbolic Cosine
  45  *
  46  * Input:
  47  *   x - floating point value
  48  *
  49  * Output:
  50  *   hyperbolic cosine of x
  51  *
  52  * Description:
  53  *   This routine returns the hyperbolic cosine of x.
  54  *
  55  *****************************************************************/
  56
  57 #include "fdlibm.h"
  58 #include "zmath.h"
  59
  60 #ifndef _DOUBLE_IS_32BITS
  61
  62 double
  63 cosh (double x)
  64 {
  65   return (sineh (x, 1));
  66 }
  67
  68 #endif /* _DOUBLE_IS_32BITS */