using System;

​

public class Program

{

    public static void Main()

    {

        Triangle t = new Triangle();

        Console.WriteLine(t.Area1(5, 6, 7));

        Console.WriteLine(t.Area2(5, 6, 120));

        Console.WriteLine(t.Area3(2, 5));

        Console.WriteLine(t.Area4(5, 6, 7, 8));

    }

​

    class Triangle

    {

        public double Area1(int a, int b, int c)

        {

            double P = (a + b + c) / 2.0;

            return Math.Sqrt(P * (P - a) * (P - b) * (P - c));

        }

​

        public double Area2(int a, int b, int angle)

        {

            return a * b * Math.Sin(angle) / 2;

        }

​

        public double Area3(int a, int h)

        {

            return (a * h) / 2.0;

        }

​

        public double Area4(int a, int b, int c, double r)

        {

            double p = (a + b + c) / 2;

            return p * r;

        }

    }

}