and the area of the triangle they enclose will be displayed.
If the points define a horizontal or vertical line,
the area is easily computed from 1/2 * base * height.
Otherwise, an enclosing rectangle is imagined,
and three right triangles outside the given triangle
(and in some cases a rectangle as well)
are subtracted from that to get the area of the triangle.
This is much simpler than using trigonometric functions or Heron's formula.
Here is an example:
The points are (0,0), (5,4), and (8,2).
The three right triangles have areas of
(5*4)/2 = 10, (2*3)/2 = 3, and (8*2)/2 = 8.
Those total 21, which when subtracted from the
enclosing 4 * 8 = 32 rectangle, leaves an area of 11
for the given triangle.
