Pythagorean Triples

Discover integer solutions of the Pythagorean theorem and how to generate them

Overview

A Pythagorean triple is a set of three natural numbers \((a, b, c)\) that can be side lengths of a right triangle.

Condition:

The triple must satisfy the Pythagorean equation:

\(\displaystyle c^2 = a^2 + b^2\)

If \(a\), \(b\), and \(c\) have no common divisor other than 1, the triple is called primitive.

Most famous example:

\((3, 4, 5)\) is the smallest primitive Pythagorean triple.




Angle bisector
Median
Altitude and the Orthocenter
Triangle bisector
Pythagorean theorem
Pythagorean triples
Circle
Square
Rectangle
Rhombus
Parallelogram
Trapezoid

Primitive and Non-Primitive Triples

Primitive

No common divisor greater than 1

Examples: \((3,4,5)\), \((5,12,13)\), \((8,15,17)\)

Non-Primitive

All numbers share a common divisor greater than 1

Examples: \((15,20,25)\), \((15,36,39)\)

Every non-primitive triple is a multiple of a primitive one.

Generation of Pythagorean Triples

A standard way to generate triples uses two integers \(m\) and \(n\), with \(m > n\):

Euclid's formulas
\(\displaystyle a = m^2 - n^2\)
\(\displaystyle b = 2mn\)
\(\displaystyle c = m^2 + n^2\)
  • Choose integers \(m > n > 0\)
  • If \(m\) and \(n\) are coprime and not both odd, the triple is primitive
  • Otherwise, the result is a non-primitive triple
Example with \(m=2\), \(n=1\)
\(a = 2^2 - 1^2 = 3\), \(b = 2\cdot2\cdot1 = 4\), \(c = 2^2 + 1^2 = 5\)

This gives the triple \((3,4,5)\).

More mathematical details are available at Wikipedia.

Key Points

  • Pythagorean triples are integer solutions of \(c^2 = a^2 + b^2\)
  • Primitive triples have greatest common divisor \(\gcd(a,b,c)=1\)
  • \((3,4,5)\) is the smallest primitive triple
  • Euclid's formulas generate infinitely many triples
  • Every non-primitive triple is a scaled primitive triple

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