PointInTriangle

using System;
using System.Collections.Generic;
using System.Linq;

namespace T2.CheckPointVsTriangle
{
    class PointInTriangle
    {
        static void Main()
        {
            Console.WriteLine("Given 3 points A, B and C, forming triangle, and a point P");
            Console.WriteLine("Check if the point P is in the triangle or not\n");

            //  triangle points
            Point a = new Point(-3.45, -2.12, 0);
            Point b = new Point(6.82, 1.9, 0);
            Point c = new Point(3.1, 10.4, 0);

 /*           Point a = new Point(1, 1, 0);
            Point b = new Point(1, 2, 0);
            Point c = new Point(2, 1, 0); */

            Vector3D va = new Vector3D(a.X,a.Y, 0);
            Vector3D vb = new Vector3D(b.X,b.Y, 0);
            Vector3D vc = new Vector3D(c.X,c.Y, 0);

            //  points to check

//            Point p = new Point(-4.8, 9.2, 0);
//            Vector3D vp = new Vector3D(p.X, p.Y, 0);

            Point p = new Point(3.2, 4.82, 0);
            Vector3D vp = new Vector3D(p.X, p.Y, 0);

//            Point p = new Point(1.9, 1.9, 0);
//            Vector3D vp = new Vector3D(p.X,p.Y,0);


            //  check if the point is in the triangle or not
            bool inTriangle = Vector3D.PointTriangle(vp, va, vb, vc);
            Console.Write("Is the point {0} inside the triangle\n\n{1} {2} {3} ? \t", p, a, b, c);
            Console.WriteLine(inTriangle);
            Console.WriteLine();
        }
    }
}

using System;

namespace T2.CheckPointVsTriangle
{
    class Vector3D
    {
        private double x;
        private double y;
        private double z;

        public double X
        {
            get
            {
                return this.x;
            }
        }

        public double Y
        {
            get
            {
                return this.y;
            }
        }

        public double Z
        {
            get
            {
                return this.z;
            }
        }

        public double Length
        {
            get
            {
                double result = Math.Sqrt(this.X * this.X + this.Y * this.Y + this.Z * this.Z);
                return result;
            }
        }

        public Vector3D(double x, double y, double z)
        {
            this.x = x;
            this.y = y;
            this.z = z;
        }

        public static Vector3D operator +(Vector3D first, Vector3D second)
        {
            double resultX = first.X + second.X;
            double resultY = first.Y + second.Y;
            double resultZ = first.Z + second.Z;
            Vector3D result = new Vector3D(resultX, resultY, resultZ);

            return result;
        }

        public static Vector3D operator -(Vector3D first, Vector3D second)
        {
            double resultX = first.X - second.X;
            double resultY = first.Y - second.Y;
            double resultZ = first.Z - second.Z;
            Vector3D result = new Vector3D(resultX, resultY, resultZ);

            return result;
        }

        public static double DotProduct(Vector3D first, Vector3D second)
        {
            double result = first.X * second.X + first.Y * second.Y + first.Z * second.Z;

            return result;
        }

        public static Vector3D CrossProduct(Vector3D first, Vector3D second)
        {
            double resultX = first.Y * second.Z - first.Z * second.Y;
            double resultY = first.Z * second.X - first.X * second.Z;
            double resultZ = first.X * second.Y - first.Y * second.X;
            Vector3D result = new Vector3D(resultX, resultY, resultZ);

            return result;
        }

        public static bool SameSide(Vector3D p, Vector3D v1, Vector3D v2, Vector3D v3)
        {
            Vector3D cp1 = CrossProduct(v2-v1, p-v1);
            Vector3D cp2 = CrossProduct(v2-v1, v3-v1);
            bool result=DotProduct(cp1, cp2) >= 0;

            return result;
        }

        public static bool PointTriangle(Vector3D p, Vector3D a, Vector3D b, Vector3D c)
        {
            bool result= SameSide(p, a, b, c) && SameSide(p, b, c, a) && SameSide(p, c, a, b);
            return result;
        }

        public override string ToString()
        {
            string result = string.Format("({0}, {1}, {2})", this.X, this.Y, this.Z);
            return result;
        }
    }
}

using System;

namespace T2.CheckPointVsTriangle
{
    class Point
    {
        public double X { get; set; }
        public double Y { get; set; }
        public double Z { get; set; }

        public Point(double x, double y, double z)
        {
            this.X = x;
            this.Y = y;
            this.Z = z;
        }

        public override string ToString()
        {
            string result = string.Format("({0}, {1})", this.X, this.Y, this.Z);
            return result;
        }
    }
}