Dear Clarice, This sounds very much like a homework problem. Is it?
In case it is, here are some hints instead of a code answer: Compute four vector for the sides. Take the dot products of the adjacent sides. If all dot products are zero, then you have shown the vertices are those of a rectangle. For the area, you have two choices 1) if it is a rectangle, then just multiply the lengths of two adjacent sides. 2) If not, sum the magnitudes of the cross products for all triangles that are part of the polygon.
If you are a student, then "it's" has a different meaning from "its". If not, never mind.
On Jun 22, 13, at 20:46 PM, clarice wrote:
> need help for this :)) > > show that the points A=(1,4), B=(7,0), C=(5,-3), D=(-1,1) are the vertices of the rectangle, find it's area. >