phpjs/functions/math/acos.js

php.js offers community built php functions in javascript

function acos(arg) {
  //  discuss at: http://phpjs.org/functions/acos/
  // original by: Onno Marsman
  //        note: Sorry about the crippled test. Needed because precision differs accross platforms.
  //   example 1: (acos(0.3) + '').substr(0, 17);
  //   returns 1: "1.266103672779499"

  return Math.acos(arg);
}