Formula
$$A = \dfrac{1}{2} \begin{vmatrix} x_1 & y_1 & 1 \\[0.3em] x_2 & y_2 & 1 \\[0.3em] x_3 & y_3 & 1 \end{vmatrix}$$
Variables
A(x1,y1)
→
Triangle vertice
B(x2,y2)
→
Triangle vertice
C(x3,y3)
→
Triangle vertice