# 物件導向QUIZ3+4+5

## Quiz3

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

namespace _106_Quiz3
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] tokens;
            Triangle tri=new Triangle();
            while (true)
            {
                Console.WriteLine("請輸入三角形的三個頂點座標，並計算其特性");
                Console.Write("(x1,y1)= ");
                tokens = Console.ReadLine().Split();
                tri.Point1X = Double.Parse(tokens[0]);
                tri.Point1Y = Double.Parse(tokens[1]);
                Console.Write("(x2,y2)= ");
                tokens = Console.ReadLine().Split();
                tri.Point2X = Double.Parse(tokens[0]);
                tri.Point2Y = Double.Parse(tokens[1]);
                Console.Write("(x3,y3)= ");
                tokens = Console.ReadLine().Split();
                tri.Point3X = Double.Parse(tokens[0]);
                tri.Point3Y = Double.Parse(tokens[1]);

                if (!tri.isValid())
                {
                    Console.WriteLine("這三點不能組成三角形!");
                }
                else
                {
                    Console.WriteLine("Perimeter=" + tri.Perimeter().ToString());
                    Console.WriteLine("Area=" + tri.Area().ToString());
                    Console.WriteLine("Radius of Circumcircle=" + tri.RadiusOfCircumcircle().ToString());
                    if (tri.isRight())
                        Console.WriteLine("直角三角形!");
                    else
                        Console.WriteLine("非直角三角形!");
                }
                Console.WriteLine("Again?  ");
                String check = Console.ReadLine();
                if ((check != "y")&&(check!="Y"))
                    break;
            }
            Console.WriteLine("End of Program!");
            Console.ReadKey();
        }
    }

}

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

namespace _106_Quiz3
{
    class Triangle
    {
        public double Point1X;
        public double Point1Y;
        public double Point2X;
        public double Point2Y;
        public double Point3X;
        public double Point3Y;

        private double SideLength(double X1, double Y1, double X2, double Y2)
        {
            return Math.Sqrt((X1 - X2) * (X1 - X2) + (Y1 - Y2) * (Y1 - Y2));
        }
        public double Perimeter()
        {

            double s1 = SideLength(Point1X, Point1Y, Point2X, Point2Y);
            double s2 = SideLength(Point2X, Point2Y, Point3X, Point3Y);
            double s3 = SideLength(Point3X, Point3Y, Point1X, Point1Y);

            return (s1 + s2 + s3);
        }
        public double Area()
        {
            double s1 = SideLength(Point1X, Point1Y, Point2X, Point2Y);
            double s2 = SideLength(Point2X, Point2Y, Point3X, Point3Y);
            double s3 = SideLength(Point3X, Point3Y, Point1X, Point1Y);
            double s = (s1 + s2 + s3) / 2;
            return Math.Sqrt(s * (s - s1) * (s - s2) * (s - s3));
        }
        public bool isValid()
        {
            double s1 = SideLength(Point1X, Point1Y, Point2X, Point2Y);
            double s2 = SideLength(Point2X, Point2Y, Point3X, Point3Y);
            double s3 = SideLength(Point3X, Point3Y, Point1X, Point1Y);
            if ((s1 + s2 <= s3) || (s2 + s3 <= s1) || (s1 + s3 <= s2))
                return false;
            return true;
        }
        public bool isRight()
        {
            double s1 = SideLength(Point1X, Point1Y, Point2X, Point2Y);
            double s2 = SideLength(Point2X, Point2Y, Point3X, Point3Y);
            double s3 = SideLength(Point3X, Point3Y, Point1X, Point1Y);
            if ((s1 * s1 + s2 * s2 - s3 * s3 < 1e-10) || (s2 * s2 + s3 * s3 - s1 * s1 < 1e-10) || (s1 * s1 + s3 * s3 - s2 * s2 < 1e-10))
                return true;
            return false;
        }
        public double RadiusOfCircumcircle()
        {
            double s1 = SideLength(Point1X, Point1Y, Point2X, Point2Y);
            double s2 = SideLength(Point2X, Point2Y, Point3X, Point3Y);
            double s3 = SideLength(Point3X, Point3Y, Point1X, Point1Y);
            double CosAlpha = (s2 * s2 + s3 * s3 - s1 * s1) / (2 * s2 * s3);
            double SinAlpha = Math.Sqrt(1 - CosAlpha * CosAlpha);
            return 0.5 * s1 / SinAlpha;
        }

    }
}

## Quiz 4

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

namespace _106_Quiz4
{
    class Program
    {
        static void Main(string[] args)
        {
            Triangle tri = new Triangle();
            string[] tokens;
            while (true)
            {
                Console.WriteLine("請依序輸入三角形的三個頂點");
                for (int i = 0; i <= 2; i++)
                {
                    Console.Write("(x" + (i + 1).ToString() + ", y" + (i + 1).ToString()+ ")= ");
                    tokens = Console.ReadLine().Split();
                    tri.XCoord[i] = Double.Parse(tokens[0]);
                    tri.YCoord[i] = Double.Parse(tokens[1]);
                }
                if (!tri.isValid())
                    Console.WriteLine("Not a Triangle, Please Input the new coordinates!");
                else
                {
                    Console.WriteLine("Perimeter=" + tri.Perimeter().ToString());
                    Console.WriteLine("Area=" + tri.Area().ToString());
                    Console.WriteLine("Radius of Circumcircle=" + tri.RadiusOfCircumcircle().ToString());
                    if (tri.isRight())
                        Console.WriteLine("This is a right triangle!");
                }
                Console.Write("Again?  ");
                String check = Console.ReadLine();
                if ((check != "y") && (check != "Y"))
                    break;
            }
            Console.WriteLine("End of Program!");
            Console.ReadKey();
        }
    }

}

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

namespace _106_Quiz4
{
    class Triangle
    {
        public double[] XCoord = new double[3];
        public double[] YCoord = new double[3];
        public const double Tol= 1e-10;
        private void SideLengths(double[] side)
        {
            //side[0] = Math.Sqrt((XCoord[0] - XCoord[1]) * (XCoord[0] - XCoord[1]) + (YCoord[0] - YCoord[1]) * (YCoord[0] - YCoord[1]));
            //side[1] = Math.Sqrt((XCoord[1] - XCoord[2]) * (XCoord[1] - XCoord[2]) + (YCoord[1] - YCoord[2]) * (YCoord[1] - YCoord[2]));
            //side[2] = Math.Sqrt((XCoord[2] - XCoord[0]) * (XCoord[2] - XCoord[0]) + (YCoord[2] - YCoord[0]) * (YCoord[2] - YCoord[0]));
            for (int i=0;i<3;i++)
            {
                side[i] = Math.Sqrt((XCoord[i] - XCoord[(i+1)%3]) * (XCoord[i] - XCoord[(i + 1) % 3]) + (YCoord[i] - YCoord[(i + 1) % 3]) * (YCoord[i] - YCoord[(i + 1) % 3]));
            }
        }
        public double Perimeter()
        {
            double[] s = new double[3];
            SideLengths(s);
            double sum = 0;

            foreach (var element in s)
                sum += element;

            return (sum);
        }
        public double Area()
        {
            double[] s = new double[3];
            SideLengths(s);
            double p = Perimeter() / 2;
            return Math.Sqrt(p * (p - s[0]) * (p - s[1]) * (p - s[2]));
        }
        public bool isValid()
        {
            double[] s = new double[3];
            SideLengths(s);
            if ((Math.Abs(s[0] + s[1] - s[2]) < Tol) || (Math.Abs(s[1] + s[2] - s[0]) < Tol) || (Math.Abs(s[2] + s[0] - s[1]) < Tol))
                return false;
            return true;
        }
        public bool isRight()
        {
            double[] s = new double[3];
            SideLengths(s);
            if ((Math.Abs(s[0] * s[0] + s[1] * s[1] - s[2] * s[2]) < Tol) || (Math.Abs(s[1] * s[1] + s[2] * s[2] - s[0] * s[0]) < Tol) || (Math.Abs(s[0] * s[0] + s[2] * s[2] - s[1] * s[1]) < Tol))
                return true;
            return false;
        }
        public double RadiusOfCircumcircle()
        {
            double[] s = new double[3];
            SideLengths(s);
            double CosAlpha = (s[1] * s[1] + s[2] * s[2] - s[0] * s[0]) / (2 * s[1] * s[2]);
            double SinAlpha = Math.Sqrt(1 - CosAlpha * CosAlpha);
            return 0.5 * s[0] / SinAlpha;
        }
    }
}

## Quiz5
private void btn_Calculate_Click(object sender, EventArgs e)
{
string message="";
Triangle tri = new Triangle();
tri.CreatePoints();
tri.ptArr[0].xCoord = Double.Parse(txtPoint1X.Text);
tri.ptArr[0].yCoord = Double.Parse(txtPoint1Y.Text);
tri.ptArr[1].xCoord = Double.Parse(txtPoint2X.Text);
tri.ptArr[1].yCoord = Double.Parse(txtPoint2Y.Text);
tri.ptArr[2].xCoord = Double.Parse(txtPoint3X.Text);
tri.ptArr[2].yCoord = Double.Parse(txtPoint3Y.Text);
if (tri.isValid())
{
if (cbx_Area.Checked)
message += ("Area=" + tri.Area().ToString() + Environment.NewLine);
if (cbx_Perimeter.Checked)
message += ("Perimeter=" + tri.Perimeter().ToString() + Environment.NewLine);
if(cbx_ShapeType.Checked)
{
switch (tri.ShapeType())
{

case 1:
message += "本三角形為直角三角形";
break;
case 2:
message += "本三角形為銳角三角形";
break;
case 3:
message += "本三角形為鈍角三角形";
break;
default:
message += "程式有錯";
break;
}
}
}
else
{
message += "此三點無法形成三角形";
}
txt_Display.Text = message;

}