The equation of tanh() can be simplified a lot

Author: infusion

functions/math/tanh.js

@@ -1,8 +1,9 @@
 function tanh(arg) {
   //  discuss at: http://phpjs.org/functions/tanh/
   // original by: Onno Marsman
+  // imprived by: Robert Eisele (http://www.xarg.org/)
   //   example 1: tanh(5.4251848798444815);
   //   returns 1: 0.9999612058841574
 
-  return (Math.exp(arg) - Math.exp(-arg)) / (Math.exp(arg) + Math.exp(-arg));
+  return 1 - 2 / (Math.exp(2 * arg) + 1);
 }