function SimpsonDef(func, a, b) {
  var c = (a + b) / 2;
  var d = Math.abs(b - a) / 6;
  return d * (func(a) + 4 * func(c) + func(b));
}
Helper function in calculating integral of a function
from a to b using simpson quadrature.

@param {Function} math function to be evaluated.
@param {Number} point to initiate evaluation.
@param {Number} point to complete evaluation.
@return {Number} evaluation.