asinh()

(PHP 4 >= 4.1.0, PHP 5, PHP 7)

反双曲正弦

说明

asinh(float $arg):float

返回$arg的反双曲正弦值，即，其双曲正弦为$arg的那个值。

参数

$arg

要处理的参数

返回值

返回$arg的反双曲正弦值

更新日志

参见

• sinh() 双曲正弦
• asin() 反正弦
• acosh() 反双曲余弦
• atanh() 反双曲正切

The correct implementation of asinh(x) for Windows plataform is:
-------------------------------------------------------
function asinh($x)
{
    return ln($x + sqrt(1 + pow($x, 2)));
}
function ln($x)
{
   return $x = log($x)/log(M_E);
}
--------------------------------------------------------
The worksheet above includes a comparation about the native asinh(x) and the implemented version using LN and LOG (like Snoyes posted on 27-Dec-2005 07:42) 
http://www.mavadesign.com.br/allan/asinh(x).xls
This implementation using LN, give THE SAME results that function asinh(x) linux native.
Allan Patrick Engel
Curitiba - Paraná - Brasil

asinh for windows:
The definition for asinh is asinh(z) = log(z + sqrt(z^2 + 1))
The built-in math functions and operators give poor results for small values of z. The BCMath version produces closer results, but still quite distant if z < 1. A BCMath version of the log function might help.
if (!function_exists("asinh")) {
  function asinh($z) {
   return log($z + sqrt($z^2 +1));
  }
}
if (!function_exists("bcasinh")) {
  function bcasinh($z) {
   return log(bcadd($z, bcsqrt(bcadd(bcpow($z, 2), 1))));
  }
}