(PHP 4 >= 4.1.0, PHP 5, PHP 7, PHP 8)

asinhInverse hyperbolic sine


asinh(float $num): float

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



The argument to process

Return Values

The inverse hyperbolic sine of num

See Also

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User Contributed Notes 2 notes

ape_cwb at yahoo dot com dot br
16 years ago
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)

This implementation using LN, give THE SAME results that function asinh(x) linux native.

Allan Patrick Engel
Curitiba - Paraná - Brasil
snoyes at gmail dot com
18 years ago
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))));
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