Find the area of the triangle. (The points are spaced 1 unit apart.)
The red triangle can be split into two triangles
Each has a base of 1......one has a height of 1 and the other has a height of 2
So...the area is
(1/2) base ( 1 + 2)
(1/2) (1) ( 3) =
3/2 units ^2 = 1.5 units^2
