How do I find the area of a triangle in 2-D if I know the coordinates of the corners?

use Heron's law:

a^2 = s(s-a)(s-b)(s-c)

a=area a,b,c = side lengths s=0.5*(a+b+c)

(works well for 3-d too)

http://www.cs.mtu.edu/~shene/COURSES...06/area-3.html

The method and the code

The three vertices are ordered in counterclockwise order, (x1,y1), (x2,y2), (x3,y3). Then,

S=0.5*(x1*(y2-y3)+x2*(y3-y1)+x3*(y1-y2))

which can be derived easily by computing a cross product of a parir (any pair) of the side vectors.

Bye

Aha! Thanks.

Hi

The very best way to do it is to calculate the cross product using two vectors (sharing the same origen)(one of the corner vertex of the triangle) which forms the edges of the triangle. Half the norm of the resulting vector will give ya the surface area AND by doing so you already calculated a normal to the surface which ye want anyhow. Just make sure your convention is correct, otherwise your normal vector might point in the wrong direction.

Cheers Barry