#include <stdio.h>
#include <stdlib.h>

int main()
{
    float AX,AY,BX,BY,CX,CY,aire,XAB,YAB,XAC,YAC;

    printf("Donner les cordonnées du triangle ABC, soit (AX;AY) et (BX;BY) et (CX;CY).\nAX=");
    scanf("%f",&AX);
    printf("AY=");
    scanf("%f",&AY);

    printf("\nBX=");
    scanf("%f",&BX);
    printf("BY=");
    scanf("%f",&BY);

    printf("\nCX=");
    scanf("%f",&CX);
    printf("CY=");
    scanf("%f",&CY);


    XAC=CX-AX;
    YAC=CY-AY;

    XAB=BX-AX;
    YAB=BY-AY;

    aire=0.5*((XAB*YAC)-(YAB*XAC));

    printf("%s%f","\nAire du triangle= ",aire);

    return 0;
}