Proposition: 3.12: Line Joining Centers of Two Circles Touching Externally
(Proposition 12 from Book 3 of Euclid's “Elements”)
If two circles touch one another externally then the (straight line) joining their centers will go through the point of union.
![fig12e](https://github.com/bookofproofs/bookofproofs.github.io/blob/main/_sources/_assets/images/euclid/Book03/fig12e.png?raw=true)
Modern Formulation
If two circles touch one another externally at a point $A$, then the straight line going through their centers goes also through $A$.
Table of Contents
Proofs: 1
Mentioned in:
Sections: 1
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References
Adapted from (subject to copyright, with kind permission)
- Fitzpatrick, Richard: Euclid's "Elements of Geometry"
Adapted from CC BY-SA 3.0 Sources:
- Prime.mover and others: "Pr∞fWiki", https://proofwiki.org/wiki/Main_Page, 2016