phpjs/functions/math/acos.js

php.js offers community built php functions in javascript

function acos(arg) {
  // From: http://phpjs.org/functions
  // +   original by: Onno Marsman
  // *     example 1: acos(0.3);
  // *     returns 1: 1.2661036727794992
  return Math.acos(arg);
}