Math question: How to compute the area of polygons

[Malte Brill]

Hi List,


this one goes out to the math experts.
How does one compute the area ( I hope it is the correct Term for
flaecheninhalt in german) of a polygon with n sides.

(That would get me started.)

I want to extract all lines of 2 polygons by analysing their points,
evaluate the area of each of them with some magic formula I don´t know ;-)
and to figure out the area of the smallest polygon surrounding both of them.

Any help will be greatly apprecheated!

Regards,

Malte