Pappus's hexagon theorem
Teorema del hexágono de Pappus
- Date
- c. 340 · confidence low
- Place
- Alexandria, Egypt
- Credited to
- Pappus of Alexandria
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What was discovered
A theorem of projective geometry: if A, B, C lie on one line and a, b, c on another, the three intersection points of the line pairs Ab-aB, Ac-aC and Bc-bC are collinear. It is one of the foundational results of projective geometry, centuries before the field was formalised.
Attributed to Pappus of Alexandria (the date of his 'Collection' is uncertain, around 320-340); regarded as one of the foundational theorems of projective geometry.
What it led to
- a seed of modern projective geometry
- special cases used in straightedge constructions
- later connections to associativity in algebraic structures (Pappian planes)