In the diagram, the four points have coordinates $A(0,1)$, $B(1,3)$, $C(5,2)$, and $D(4.5,0)$. What is the area of quadrilateral $ABCD$?
[ABCD] = [ EFGH] - [EBA] - [ FCB] - [CGD] - [ ADH]
[ABCD ] = (5 *3) - (1/2) [ 1 *2 + 4*1 + 2* (1/2) + 4.5 *1 ] =
15 - (1/2) [ 2 + 4 + 1 + 4.5 ] =
15 - (1/2) [ 11.5 ] =
15 - 11.5 / 2 =
[30 - 11.5 ] / 2 =
9.25
+1248 
