public void TestPiCalculation()
        {
            Func <double, double> function = (x) => { return(1 / (1 + x * x)); };
            double integral = function.PIntegral1(0, 1, eps);

            Assert.IsTrue(Math.Abs(Math.PI - 4 * integral) < eps * 10);
        }
        public void TestSimplePIntegral()
        {
            Func <double, double> function = (x) => { return(x * x); };
            double integralResult          = function.PIntegral1(0, 10, eps, 10);

            Assert.IsTrue(Math.Abs(integralResult - 1000 / (double)3) <= eps);
        }