Method getFirst

src/test/Derivative.java:51–53

Direct application of first derivative method. @param f @param x @param h @return

(final DoubleUnaryOperator f, double x, double h)

	 * @return
	 */
	static public double getFirst(final DoubleUnaryOperator f, double x, double h) {
		return (f.applyAsDouble(x + h) - f.applyAsDouble(x - h)) / h / 2.0;
	}

	/**
	 * First derivative wrapped to re-assign one of the two parameters.