program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication3
{
    class Cartesian
    {
        double x;
        double y;

        public Cartesian() { }

        public Cartesian(double x, double y)
        {
            this.x = x;
            this.y = y;
        }

        public double GetX()
        {
            return x;
        }

        public void SetX(double x)
        {
            this.x = x;
        }

        public double GetY()
        {
            return y;
        }

        public void SetY(double y)
        {
            this.y = y;
        }

        public Polar ToPolar()
        {
            var v = Math.Sqrt(Math.Pow(x, 2) + Math.Pow(y, 2));
            var a = Math.Atan(y / x) * (180 / Math.PI);

            return new Polar(v, a);
        }

        public static Cartesian Add(Cartesian A, Cartesian B)
        {
            return new Cartesian(A.GetX() + B.GetX(), B.GetX() + B.GetY());
        }

        public static Cartesian Subtract(Cartesian A, Cartesian B)
        {
            return new Cartesian(A.GetX() - B.GetX(), B.GetX() - B.GetY());
        }

        public static Cartesian Multiply(Cartesian A, Cartesian B)
        {
            var Pa = A.ToPolar();
            var Pb = B.ToPolar();

            return Polar.Multiply(Pa, Pb).ToCartesian();
        }

        public static Cartesian Divide(Cartesian A, Cartesian B)
        {
            var Pa = A.ToPolar();
            var Pb = B.ToPolar();

            return Polar.Divide(Pa, Pb).ToCartesian();
        }
    }

    class Polar
    {
        double v;
        double a;

        public Polar() { }

        public Polar(double v, double a)
        {
            this.v = v;
            this.a = a;
        }

        public double GetV()
        {
            return v;
        }

        public void SetV(double v)
        {
            this.v = v;
        }

        public double GetA()
        {
            return a;
        }

        public void SetA(double a)
        {
            this.a = a;
        }

        public Cartesian ToCartesian()
        {
            var x = v * Math.Cos(a * (Math.PI / 180));
            var y = v * Math.Sin(a * (Math.PI / 180));

            return new Cartesian(x, y);
        }

        public static Polar Add(Polar A, Polar B)
        {
            var Ca = A.ToCartesian();
            var Cb = B.ToCartesian();

            return Cartesian.Add(Ca, Cb).ToPolar();
        }

        public static Polar Subtract(Polar A, Polar B)
        {
            var Ca = A.ToCartesian();
            var Cb = B.ToCartesian();

            return Cartesian.Subtract(Ca, Cb).ToPolar();
        }

        public static Polar Multiply(Polar A, Polar B) {
            return new Polar(A.GetV() * B.GetV(), A.GetA() + B.GetA());
        }

        public static Polar Divide(Polar A, Polar B)
        {
            return new Polar(A.GetV() / B.GetV(), A.GetA() - B.GetA());
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var Vi = new Polar(10, 30); // 10|_30
            double W = 500; // [rad/sec]
            double R = 100; // [Ohm]
            double L = 0.1; // [Hy]

            Cartesian Xl = new Cartesian(0, W * L);
            Cartesian Z = Cartesian.Add(new Cartesian(R, 0), Xl);
            Cartesian I = Cartesian.Divide(Vi.ToCartesian(), Z);
            Cartesian Vr = Cartesian.Multiply(I, new Cartesian(R, 0));
            Cartesian Vl = Cartesian.Multiply(I, Xl);

            while (true)
            {
                Console.ForegroundColor = ConsoleColor.Yellow;
                Console.WriteLine("1) Z\n2) I\n3) Vr\n4) Vl");
                Console.ForegroundColor = ConsoleColor.Green;
                Console.Write("Make a decision: ");
                int i;
                if (!int.TryParse(Console.ReadLine(), out i)) continue;

                switch (i)
                {
                    case 1:
                        Print("Z", Z);
                        break;

                    case 2:
                        Print("I", I);
                        break;

                    case 3:
                        Print("Vr", Vr);
                        break;

                    case 4:
                        Print("Vl", Vl);
                        break;
                }
            }
        }

        private static void Print(string A, Cartesian B)
        {
            Console.ForegroundColor = ConsoleColor.Red;
            Console.WriteLine("{0} = {1}+{2}j OR {0} = {3}({4})\n", A, B.GetX(), B.GetY(), B.ToPolar().GetV(), B.ToPolar().GetA());
        }
    }
}