Friday, March 12, 2021

Additional Thoughts on the Pythagorean Triple Generator



A prior post list a formula for producing PythagoreanTriples. A Pythagorean Triple is a set of three integers (a, b, c) that will form a right angle triangle. The formula is:

Let n and m be any positive integers where n>m. The Pythagorean Triple generated is formed by the numbers:
2nm
n
2 - m2
n
2 +m2

This prior post did not state way this formula works. We can show why in just a few steps. The two requirements for a Pythagorean Triple (a, b, c) are that a, b, and c are integers and that a2 + b2 = c2.

For the first requirement, we need to show that 2nm,  n2 - m2 , and  n2 +m2 are all integers. It is given that n and m are integers, Since both n and m are integers, a product of two integers is an integer and 2 times an integer is an integer, so 2nm is an integer. Likewise, for n2 - m2
and n
2 +m2, we are only dealing with squares of integers, their sums and their differences. All these operations will produce only integers, therefore n2 - m2 and n2 +m2 are also integers.

For the second requirement, we need to show that (2nm)2 + (n2 - m2)2 = (n2 +m2)2

Expanding the left-hand side,

 (2nm)2 + (n2 - m2)2 = 4n2m2 + n4 – 2n2m2 + m4

Simplifying and reordering,       

                              = n4 + 2n2m2 + m4

Compare this result to squaring the original right-hand side, we see the Pythagorean Triple generator formula will produce triples that meet the requirements of being proper Pythagorean Triples.

(n2 +m2)2 = n4 + 2n2m2 + m4

Update 9/24/2022: A spreadsheet has been created to produce these triples.

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