using System;

​

public class Program // ЗАДАЧА 5

{

    public static void Main()

    {

        Triangle t = new Triangle();

        t.Area1(3, 6);

    }

}

​

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 - a) * (p - b) * (p - c));

    }

​

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

    {

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

    }

​

    public double Area3(int a, int b, int c, int h, int R)

    {

        return a * b * c / (double)(4 * R);

    }

​

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

    {

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

        return p * r;

    }

}