Proposition: Prop. 11.15: Planes through Parallel Pairs of Meeting Lines are Parallel
(Proposition 15 from Book 11 of Euclid's “Elements”)
If two straight lines joined to one another are parallel (respectively) to two straight lines joined to one another, which are not in the same plane, then the planes through them are parallel (to one another).
 For let the two straight lines joined to one another, $AB$ and $BC$, be parallel to the two straight lines joined to one another, $DE$ and $EF$ (respectively), not being in the same plane.
 I say that the planes through $AB$, $BC$ and $DE$, $EF$ will not meet one another (when) produced.
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 BYSA 3.0 Sources:
 Prime.mover and others: "Pr∞fWiki", https://proofwiki.org/wiki/Main_Page, 2016