Math Is Fun Forum

boy15

Member

Registered: 2010-03-29

Posts: 16

dual of 27-gon?

Hey everyone, can anybody help me out here, I don't know what the dual of a regular 27-gon is.

Thanks

Bob

Administrator

Registered: 2010-06-20

Posts: 10,235

Re: dual of 27-gon?

Hi boy15

I'm not too sure I understand the question yet.  Trouble is, the word 'dual' is used a lot in maths and can mean many things. 

It sounds like you're trying to construct another 2D shape from the polygon. 
See http://en.wikipedia.org/wiki/Duality_(mathematics)
and then part way down the page 'Dimension-reversing dualities'.

This shows how to make the dual in 3D and 2D.  If this is what you want then follow the rules:

(i)  Put a point anywhere inside the polygon and another anywhere outside. [In general one point in each region of the shape.]

(ii) Join every point to every other point once for each side that you cross.

For a 27-gon you would end up with 27 lines coming from the inside point and going to the outside point, each one crossing a side.

If that's not what you wanted, I suggest you post an example where you know the answer so we can see what you're trying to do.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

boy15

Member

Registered: 2010-03-29

Posts: 16

Re: dual of 27-gon?

That helped alot. Thanks again Bob.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,235

Re: dual of 27-gon?

You're welcome.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob