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   Joined Pythagorean Triangles
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   Author  Topic: Joined Pythagorean Triangles  (Read 587 times)
ThudnBlunder
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Joined Pythagorean Triangles   Pythag.jpg
« on: Sep 25th, 2007, 4:38pm »
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The figure below shows two Pythagorean triangles joined together with a common side. Can you find any more examples where three of the five side-lengths are prime?
« Last Edit: Sep 26th, 2007, 5:05am by ThudnBlunder » IP Logged


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Re: Joined Pythagorean Triangles   Pythag2.jpg
« Reply #1 on: Sep 25th, 2007, 4:45pm »
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Can a fourth triangle be added (as below) such that four of the seven side-lengths are prime?
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Barukh
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Re: Joined Pythagorean Triangles  
« Reply #2 on: Sep 25th, 2007, 11:55pm »
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For the first: yes, for example: a = 11, c = 61, e = 1861.
« Last Edit: Sep 26th, 2007, 8:56am by Barukh » IP Logged
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Re: Joined Pythagorean Triangles  
« Reply #3 on: Sep 26th, 2007, 12:07am »
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For the second: yes, a > 100.
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towr
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Re: Joined Pythagorean Triangles  
« Reply #4 on: Sep 26th, 2007, 3:01am »
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Are there also examples with two triangles where 4 of the 5 sides are prime? (In which case, obviously, the even sides have to match).
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ThudnBlunder
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Re: Joined Pythagorean Triangles  
« Reply #5 on: Sep 26th, 2007, 4:13am »
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on Sep 25th, 2007, 11:55pm, Barukh wrote:
For the first: yes, for example: a = 11, b = 61, e = 1861.

But a and b are not defined in the first problem.   Tongue
 
on Sep 26th, 2007, 12:07am, Barukh wrote:
For the second: yes, a > 100.

a = 101?  Roll Eyes
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Re: Joined Pythagorean Triangles  
« Reply #6 on: Sep 26th, 2007, 4:18am »
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on Sep 26th, 2007, 4:13am, ThudanBlunder wrote:
a = 101?  Roll Eyes

No, a > 101.  Tongue
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Re: Joined Pythagorean Triangles  
« Reply #7 on: Sep 26th, 2007, 6:57am »
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on Sep 25th, 2007, 11:55pm, Barukh wrote:
For the first: yes, for example: a = 11, b = 61, e = 1861.

If a is prime, can you express the other sides in terms of it?
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Re: Joined Pythagorean Triangles  
« Reply #8 on: Sep 26th, 2007, 8:58am »
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on Sep 26th, 2007, 6:57am, ThudanBlunder wrote:
If a is prime, can you express the other sides in terms of it?

There was a typo in notation.
 
c = F(a) = (a2+1)/2, e = F(c)
 
Of course, this is necessary, but not sufficient.
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