Find the area based on the coordinates of three points in the plane

official

• Set the coordinates of three points,$A(a,b),B(c,d),C(e,f)$, then the area of ​​the triangle is
  

  $$S=|ad＋be＋cf－af－bc－de|/2 = \frac{1}{2}|\left( {\begin{array}{*{20}{c}} a&b&1\\ c&d&1\\ e&f&1 \end{array}} \right)|$$

• Reference link: https://wenku.baidu.com/view/4dc519202f60ddccda38a09d.html