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Proposition 19

Given three numbers, to investigate when it is possible to find a fourth proportional to them.
| Let A, B, and C be the given three numbers. It is required to investigate when it is possible to find a fourth proportional to them.
[The Greek text of this Proposition is corrupt. However, analogously to Proposition 18 the condition that a fourth proportional to A, B, and C exists is that A measure the product of B and C. ]
Q.E.D.

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(Forthcoming)

Book IX Introduction - Proposition IX.18 - Proposition IX.20.

© 1996
D.E.Joyce
Clark University