Remove obsolete math polyfills

src/PhpSpreadsheet/Calculation/Functions.php

@@ -673,32 +673,6 @@ class Functions
     }
 }
 
-//
-//    There are a few mathematical functions that aren't available on all versions of PHP for all platforms
-//    These functions aren't available in Windows implementations of PHP prior to version 5.3.0
-//    So we test if they do exist for this version of PHP/operating platform; and if not we create them
-//
-if (!function_exists('acosh')) {
-    function acosh($x)
-    {
-        return 2 * log(sqrt(($x + 1) / 2) + sqrt(($x - 1) / 2));
-    }    //    function acosh()
-}
-
-if (!function_exists('asinh')) {
-    function asinh($x)
-    {
-        return log($x + sqrt(1 + $x * $x));
-    }    //    function asinh()
-}
-
-if (!function_exists('atanh')) {
-    function atanh($x)
-    {
-        return (log(1 + $x) - log(1 - $x)) / 2;
-    }    //    function atanh()
-}
-
 //
 //    Strangely, PHP doesn't have a mb_str_replace multibyte function
 //    As we'll only ever use this function with UTF-8 characters, we can simply "hard-code" the character set