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

- Let $ABC$ be a circle, and let $BEC$ be an angle at its center, and $BAC$ (one) at (its) circumference.
- And let them have the same circumference base $BC$.
- I say that angle $BEC$ is double (angle) $BAC$.

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]

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

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

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