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Pythagorean triplet (Definition)

A Pythagorean triplet is a set $ \{a, b, c\}$ of three positive integers such that

$\displaystyle a^2 + b^2 = c^2. $

That is, $ \{a, b, c\}$ is a Pythagorean triplet if there exists a right triangle whose sides have lengths $ a$, $ b$, and $ c$, respectively. For example, $ \{3, 4, 5\}$ is a Pythagorean triplet. Given one Pythagorean triplet $ \{a, b, c\}$, we can produce another by multiplying $ a$, $ b$, and $ c$ by the same factor $ k$. It follows that there are countably many Pythagorean triplets.

Primitive Pythagorean triplets

A Pythagorean triplet is primitive if its elements are coprimes. All primitive Pythagorean triplets are given by

$\displaystyle a$ $\displaystyle =$ $\displaystyle 2mn,$  
$\displaystyle b$ $\displaystyle =$ $\displaystyle m^2\!-\!n^2,$  
$\displaystyle c$ $\displaystyle =$ $\displaystyle m^2\!+\!n^2,$  

where the seed numbers $ m$ and $ n$ are any two coprime positive integers, one odd and one even, such that $ m > n$.

Note. One can form the sequence (Sloane's A100686)

$\displaystyle 1,\,2,\,3,\,4,\,7,\,24,\,527,\,336,\,164833,\,354144,\,... $
taking first the seed numbers 1 and 2 which give the legs 3 and 4, taking these as new seed numbers which give the legs 7 and 24, and so on.



"Pythagorean triplet" is owned by drini. [ full author list (4) | owner history (1) ]
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See Also: Pythagorean theorem, incircle radius determined by Pythagorean triple

Other names:  Pythagorean triple
Also defines:  seed number, primitive Pythagorean triple, primitive Pythagorean triplet
Keywords:  Triangle, Pythagoras, Geometry

Attachments:
proof of Pythagorean triplet (Proof) by Thomas Heye
proof of Pythagorean triples (Proof) by fredlb
first primitive Pythagorean triplets (Example) by pahio
proof of Pythagorean triples (Proof) by rm50
rational sine and cosine (Theorem) by pahio
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Cross-references: legs, sequence, even, odd, coprimes, primitive, factor, lengths, sides, right triangle, integers, positive
There are 9 references to this entry.

This is version 8 of Pythagorean triplet, born on 2001-10-06, modified 2007-11-06.
Object id is 138, canonical name is PythagoreanTriple.
Accessed 15184 times total.

Classification:
AMS MSC11-00 (Number theory :: General reference works )

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