Beg your help, the great god,

CodePudding user response:

When the three points A, B, C respectively, the coordinates of A (x1, y1), B (x2, y2), C (x3, y3), for the triangle area,

S=(x1y2 - x1y3 + x2y3 x2y1 + x3y1 - x2y2),