# Calculate square of irregular shape

How to calculate square of shape shown below? Note that the only given information is length of each side. If it is convex, just generate trangle fan list, and sum area of each triangle.

Can you explain your homework needs ?

ZbuffeR
I doesn’t have any points to use triangles, as I depicted the only info is length of each side of the polygon, coordinates of points of the polygon are unknown. If I know each point then I wouldn’t ask such a question.

The task is not a homework, the picture shows approximate lengths of a sides of a house of my grandparents, its long story involwing law. I thought I’d not talk everyting out because it’s rather private topic and not concerning this thread…

The question is rather mathematical and not concering OpenGL. Once more I doesn’t have any points, nor I have any angles, whatever etc. The only info I have is length of sides of the polygon. Is it possible to calculate square with only that info? I was googling some info but the best I found is stating that this is impossible, isn’t it?

How can you possibly say you don’t have angles? You have a figure, you can take approximate angles from it. It is not as if you need an area accurate down to a mm^2.

If all you have is the length like this, it’s hard to calculate the area, what you need is to basically split it into triangles and then measure those lengths inside if at all possible.
If not then you have to use something like google maps to get the rough outline, however that can only be as accurate as you can approximate the angles.

There appears to not be enough information to solve this. You need a scale drawing that you can make accurate measurements with in a CAD program for example. I came up with this pretty quick, which isn’t perfectly accurate but close: Now just use Heron’s formula to calculate the area of each triangle:

[P=a+b+c/2](http://www.bcthund.net/cgi-bin/mimetex.cgi?\Huge p=\frac{a+b+c}{2})
[A=sqrt(P(P-a)(P-b)(P-c))](http://www.bcthund.net/cgi-bin/mimetex.cgi?\Huge A=\sqr{p(p-a)(p-b)(p-c)})

bcthund
Thanks for a good suggestion, I’ll try that, what the program you use by the way?

To all:
Thanks for a suggestions! It seems that indeed there isn’t enought information to solve this problem, I’ll check carefully what I can do with angles and google maps and then I’ll repost. I think I’ll respond in week, I’m currently not near home.

I used QCad, I use it for all my drafting. It isn’t a polished product like AutoCAD but it’s free and available in the software repository for linux. They have source files available on their website for the free community edition.

The problem is solved now, actually we haven’t even used google maps or angles, it turned out that we alredy have coordinates of points of the the shape and angles - I was uninformed about this. So now calculating area is no problem, thought it was no problem even before, but now its easier 