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.
Eugenio Beltrami
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Eugenio Beltrami was an Italian mathematician notable for his work concerning differential geometry and mathematical physics. His work was noted especially for clarity of exposition. He was the first
Eugenio Beltrami
Sulla teoria dell'induzione magnetica secondo Poisson, 1884