find area of triangle with 3 points known

please can someone help me find the area from the triangular region shown in the image...

http://oi59.tinypic.com/2jag575.jpg

i know the xmin, xmax and ymax values.... but with these values how to find the area of a triangle.... please do help me...

Answer 1

[Roger Stafford]

If I interpret the figure correctly, the area is:

   a = 1/2*(xmax-xmin)*ymax;

In general a triangle's area is one-half its base times its height.

[Sean de Wolski]

Or

doc polyarea