Find the area of the triangle whose vertices are (3, 8), (-4, 2) and (5,
1).
Solution
The area of triangle is given by \(\Delta=\frac{1}{2}|\begin{smallmatrix}3&8&1\\
-4&2&1\\ 5&1&1\end{smallmatrix}|\)\(=\frac{1}{2}[3(2-1)-8(-4-5)+1(-4-10)]\)\(=\frac{1}{2}(3+72-14)=\frac{61}{2}\)
