The corners \( (x_1,y_1) \)
and \( (x_2,y_2) \)
and \( (x_3, y_3) \)
of a triangle.
If \( (x_3,y_3)=(0,0) \)
The area of the triangle
\(
=
\frac{1}{2}
\begin{vmatrix}
x_1 & y_1 \\
x_2 & y_2
\end{vmatrix}
\)
otherwise,
area
\(
=
\frac{1}{2}
\begin{vmatrix}
x_1 & y_1 & 1 \\
x_2 & y_2 & 1 \\
x_3 & y_3 & 1 \\
\end{vmatrix}
\)
the area of the parallelogram: