Riemann Sum

	/**
	 * @see <a href="http://en.wikipedia.org/wiki/Riemann_sum#Middle_sum">http://en.wikipedia.org/wiki/Riemann_sum#Middle_sum</a>
	 */
	public static double riemannSum(Function<Double, Double> func, double beginPoint, double endPoint, double interval){
		double result = 0;
		//Middle Sum(Maybe error sum is most minimal)
		for(double x = beginPoint; x<=endPoint; x+=interval){
			result += func.apply(x+interval/2);
		}
		result *= interval;

		return result;
	}