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Proposition: 3.20: Inscribed Angle Theorem

(Proposition 20 from Book 3 of Euclid’s “Elements”)

In a circle, the angle at the center is double that at the circumference, when the angles have the same circumference base.

Modern Formulation

The central angle is double the inscribed angle.

| | | | | created: 2016-08-01 11:01:23 | modified: 2019-03-30 00:36:52 | by: bookofproofs | references: [6419], [6908]

1.Proof: (related to "3.20: Inscribed Angle Theorem")

Edit or AddNotationAxiomatic Method

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[6908] Prime.mover and others: “Pr∞fWiki”, https://proofwiki.org/wiki/Main_Page, 2016

Freely downloadable

[6419] Fitzpatrick, Richard: “Euclid’s Elements of Geometry”, http://farside.ph.utexas.edu/Books/Euclid/Euclid.html, 2007

Bibliography (further reading)

(none)