\( F=\frac{1}{2}\left|\operatorname{det}\left(\begin{array}{ccc} 1 & 1 & 1 \\ p_{11} & p_{12} & p_{13} \\ p_{21} & p_{22} & p_{23} \end{array}\right)\right| \) =
\( \frac{1}{2}\left|1 \cdot \operatorname{det}\left(\begin{array}{ccc} p_{12} & p_{13} \\ p_{22} & p_{23} \end{array}\right)-1\cdot\operatorname{det}\left(\begin{array}{ccc} p_{11} & p_{13} \\ p_{21} & p_{23} \end{array}\right)+ 1\cdot\operatorname{det}\left(\begin{array}{ccc} p_{11} & p_{12} \\ p_{21} & p_{22} \end{array}\right) \right| \)
\( \frac{1}{2}\left|\operatorname{det}\left(\vec{p}_{2}, \vec{p}_{3}\right)-\operatorname{det}\left(\vec{p}_{1}, \vec{p}_{3}\right)+ \operatorname{det}\left(\vec{p}_{1}, \vec{p}_{2}\right) \right| \)
Das war schon mal der erste Teil.