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243:(in which you need to toss out both Euclid's second and fifth postulates) it can be shown that the summit angles of a Saccheri quadrilateral are obtuse. This is what the article is saying without mentioning the additional modifications needed to make the statement true. So, the answer to your question is, they both are ... but under different sets of assumptions.
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According to Cooke's history of math text, Jeremy Gray calls this a Thabit quadrilateral and that it thus predates
Khayyam by a few centuries. If so, perhaps some Knowledge guru could fix that; I am not familiar enough with the editing protocol and syntax to do so myself without spending more time
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I can see why you are confused. The article is not being precise enough to clarify this. The assumption of the obtuse angle,
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This new page is to direct article text links of "Saccheri quadrilateral" to the "Saccheri
Quadrilateral" article.
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This article claims that in the case of obtuse angle, the quadrilateral leads to elliptical geometry, but both
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than I can devote to it. But it would be good to have the right people attributed to this concept.
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on
Knowledge. If you would like to participate, please visit the project page, where you can join
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218:) state (without proof) that this case leads to accept the fifth postulate. Which is correct?--
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Capitalization matters in Wiki article links... perhaps to be considered a
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in the presence of the first four
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