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# asinh

(PHP 4 >= 4.1.0, PHP 5)

asinhInverse hyperbolic sine

### Description

float asinh ( float \$arg )

Returns the inverse hyperbolic sine of arg, i.e. the value whose hyperbolic sine is arg.

### Parameters

arg

The argument to process

### Return Values

The inverse hyperbolic sine of arg

### Changelog

Version Description
5.3.0 This function is now available on all platforms

User Contributed Notes
asinh
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 - ParanĂ¡ - Brasil```
Arakrys
08-Jun-2007 07:57
`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))));     } }```