The area of a triangle with vertices $(a, b), (c, d)$, and $(e, f)$ is:

$\pm \frac{1}{2}\left| \begin{array}{c c c}a&b&1\\c&d&1\\e&f&1\end{array}\right|$

Note: You will need to use a calculator to evaluate this determinant.

To compute the area of a parallelogram using a determinant, two vectors are needed.
Write two vectors, one from the first point to the second point and another from the first point to the third point.