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**razor****Member**- Registered: 2006-02-24
- Posts: 6

we have a pentagram.How we can with two lines create nine not covertly triangles?

*Last edited by razor (2006-02-25 13:47:57)*

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,626

I am not sure what "not covertly" means, but my biggest problem is: how is it possible to get nine triangles with only two lines? Best I can do is 5. I can get 9 with three lines!

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**ashwil****Member**- Registered: 2006-02-27
- Posts: 121

Trick question!

A penta**gram** already has 5 triangles within it. Joining any two pairs of alternate nodes on the inner penta**gon** will create 3 new triangles within the central pentagon and one more with one of the extarnal points. Total 9.

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**ashwil****Member**- Registered: 2006-02-27
- Posts: 121

Scrub that last post! That method actually creates 12 triangles!!

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**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,905

Here's what I get:

*Last edited by krassi_holmz (2006-03-01 04:25:35)*

IPBLE: Increasing Performance By Lowering Expectations.

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,626

Penta**gram** ... I should read more careully!

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**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

I agree with what krazzi has.

Why did the vector cross the road?

It wanted to be normal.

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**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,905

Now the other main question: are there another combinations?

For which numbers it is possible to cut the pentagram(or we may start with circle) with k lines?

Hm... Interesting.

IPBLE: Increasing Performance By Lowering Expectations.

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