#include<stdio.h>
#include<math.h>
#include<conio.h>
int main ()
{
	printf("De: Nhap toa do 4 diem A,B,C,D kiem tra xem D co thuoc tam giac ABC khong\n");
	printf("------------------------------------------\n");
	//Khoi tao bien
	float xA,xB,xC,xD,yA,yB,yC,yD;
	float S1,S2,S3,S,p,p1,p2,p3,AB,AC,AD,BC,BD,CD;
	//Tinh toan
	printf("Nhap xA:");scanf("%f",&xA);
	printf("Nhap yA:");scanf("%f",&yA);
	printf("Nhap xB:");scanf("%f",&xB);
	printf("Nhap yB:");scanf("%f",&yB);
	printf("Nhap xC:");scanf("%f",&xC);
	printf("Nhap yC:");scanf("%f",&yC);
	printf("Nhap xD:");scanf("%f",&xD);
	printf("Nhap yD:");scanf("%f",&yD);
	AB=sqrt((pow(xB-xA,2))+pow(yB-yA,2));
	AC=sqrt((pow(xC-xA,2))+pow(yC-yA,2));
	AD=sqrt((pow(xD-xA,2))+pow(yD-yA,2));
	BD=sqrt((pow(xD-xB,2))+pow(yD-yB,2));
	BC=sqrt((pow(xC-xB,2))+pow(yC-yB,2));
	CD=sqrt((pow(xD-xC,2))+pow(yD-yC,2));
	p=(AB+BC+AC)/2;
	p1=(AB+BD+AD)/2;
	p2=(AD+CD+AC)/2;
	p3=(BC+BD+CD)/2;
	S=sqrt(p*(p-AB)*(p-AC)*(p-BC));
	S1=sqrt(p1*(p1-AB)*(p1-BD)*(p1-AD));
	S2=sqrt(p2*(p2-AD)*(p2-CD)*(p2-AC));
	S3=sqrt(p3*(p3-BC)*(p3-BD)*(p3-CD));
	if (S==(S1+S2+S3)){
		printf("D nam trong tam giac ABC");
	}
	if (S>(S1+S2+S3)){
		printf("D nam ngoai tam giac ABC");
	}
	return 0;
}