Parallel postulate
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In geometry, the parallel postulate is the fifth postulate in Euclid's Elements and a distinctive axiom in Euclidean geometry. It states that, in two-dimensional geometry:
The page containing the Parallel Postulate from the 1747 Latin edition of Euclid’s Elements, originally Euclid’s 5th Postulate, here reclassified and presented as Axiom XII by the editor.
Euclidean geometry
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Euclidean geometry is a mathematical system attributed to Euclid, an ancient Greek mathematician, which he described in his textbook on geometry, Elements. Euclid's approach consists in assuming a sma
Parallel postulate
…In geometry, the parallel postulate is the fifth postulate in Euclid's Elements and a distinctive axiom in Euclidean geometry. It states that, in two-dimensional geometry: If a straight line intersects two other straight lines forming two interior angles on the same side that…
Detail from Raphael's The School of Athens featuring a Greek mathematician – perhaps representing Euclid or Archimedes – using a compass to draw a geometric construction.
3D CAD model
PCB of a DVD player
NASA Cassegrain, extremely high gain ~70 dBi.