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。

注: 本函数未在 Windows 平台下实现。

参见: asin()acosh(),和 atanh()


add a note add a note User Contributed Notes
snoyes at gmail dot com
27-Dec-2005 11:42
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))));
   }
}