Math 函数
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asinh

(PHP 4 >= 4.1.0, PHP 5)

asinh — 反双曲正弦

说明

float asinh ( float $arg )

返回 arg 的反双曲正弦值，即，其双曲正弦为 arg 的那个值。

参见： asin()， acosh()，和 atanh()。

参数

arg

The argument to process

返回值

The inverse hyperbolic sine of arg

更新日志

版本 说明
5.3.0 This function is now available on all platforms

参见

Math 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: 反双曲正弦

用户评论:

ape_cwb at yahoo dot com dot br (15-Nov-2007 01:40)

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

Arakrys (08-Jun-2007 08:57)

When using snoyes alternative bcasinh function, don't forget to check the precision of each single bcfunction or the default precision of ini setting bcmath.scale.

snoyes at gmail dot com (27-Dec-2005 03:42)

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))));
    }
}