function to calculate area of triangle
float area ( int x1 , int y1 , int z1 , int x2 , int y2 , int z2 ) { float area = sqrt ( pow ( ( y1 * z2 - y2 * z1 ) , 2 ) + pow ( ( x1 * z2 - x2 * z1 ) , 2 ) + pow ( ( x1 * y2 - x2 * y1 ) , 2 ) ) ; area = area / 2 ; return area ; }