Determine the area of the quadrilateral whose vertices are (1,3), (6,5), (9,1) and (3,-3).
HI sharkman ,
THe area would be ,
$\displaystyle
A=\frac{1}{2}\vert\begin {pmatrix} 1 & 6 & 9 & 3 & 1 \\ 3 & 5 & 1 & -3 & 3 \end {pmatrix}\vert
$
Gosh , i have a problem typing matrix . sorry if its a bit messy . Generally , if you are asked to find the areas of triangle or quadrilateral given their vertices, you can do that . DO you know how to get its determinant ?