Abstract
We prove that, in Hilbert's plane absolute geometry, an axiom used by Lagrange in a proof of the Euclidean parallel postulate in a paper read on 3 February 1806 at the Institut de France, which states that "If a and b are two parallels from P to g, then the reflection of a in b is parallel to g as well", is equivalent to F. Bachmann's Lotschnittaxiom, which states that "The perpendiculars on the sides a right angle always intersect."
Original language | English (US) |
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Pages (from-to) | 165-171 |
Number of pages | 7 |
Journal | Journal of Geometry |
Volume | 95 |
Issue number | 1-2 |
DOIs | |
State | Published - Dec 15 2009 |
Keywords
- Absolute geometry
- Bachmann's Lotschnittaxiom
- Lagrange's axiom
- Metric planes
ASJC Scopus subject areas
- Geometry and Topology