Formula ariei triunghiului
Aria triunghiului ABC cu vârfurile \(A\left ( x_{1},y_{1} \right ),B\left ( x_{2},y_{2} \right ),C\left ( x_{3},y_{3} \right )\) este:
\(A= \frac{1}{2}\left | x_{1}\left ( y_{3}-y_{2} \right )+x_{2}\left ( y_{1}-y_{3} \right ) +x_{3}\left ( y_{2}-y_{1} \right )\right |\).
\(A= \frac{1}{2}\left | x_{1}\left ( y_{3}-y_{2} \right )+x_{2}\left ( y_{1}-y_{3} \right ) +x_{3}\left ( y_{2}-y_{1} \right )\right |\).