Proposition: Prop. 9.19: Condition for Existence of Fourth Number Proportional to Three Numbers
Euclid's Formulation
For three given numbers, to investigate when it is possible to find a fourth (number) proportional to them.
- Let $A$, $B$, $C$ be the three given numbers.
- And let it be required to investigate when it is possible to find a fourth (number) proportional to them.
![fig19e](https://github.com/bookofproofs/bookofproofs.github.io/blob/main/_sources/_assets/images/euclid/Book09/fig19e.png?raw=true)
Modern Formulation
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Table of Contents
Proofs: 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