double a = 1, b = 4,n = 52;
            double h = (b - a) / n;
            double x = a, sum = 0;
            double S = 0;
            double ln_x =
            double y = Math.Pow(Math.Log(x), 2) / x;
            double ya = Math.Pow(Math.Log(a), 2) / a;
            double yb = Math.Pow(Math.Log(b), 2) / b;
            for (int i = 1; i <= n - 1; i++)
            {
                x = x + h;
                sum = sum + y;
            }
            S = (ya + yb + 2 * sum) * (h / 2);

            Console.WriteLine(y);

            Console.WriteLine("Величина определенного интеграла ln^2(x)/x равна {0}",S);

            //double F = Math.Pow(Math.Log(x), 3) / 3;
            double Fa = Math.Pow(Math.Log(a), 3) / 3;
            double Fb = Math.Pow(Math.Log(b), 3) / 3;
            double Sprov = Fb - Fa;

            Console.WriteLine(Fa);

            Console.WriteLine("Проверка численным методом - {0}", Sprov);