Index --- introduction --- definitions --- axioms and postulates --- propositions --- other
Euclid wrote in Greek, but several terms now used in Euclid are in Latin. Here are their meanings.
|Pons Asinorum||Bridge of Asses||Name of Proposition 5. The name could be because the diagram ends up looking a little like a bridge, or because since it is slightly harder than previous proofs, this is the point that 'asses' fall off!|
(quod erat demonstrandum)
|That which was to be proved||In other words - we've done it! It is the traditional end to a proof.|
(quod erat faciendum)
|That which was to be done||In other words - we've done it! It is the traditional end to a construction.|
|Reductio ad absurdum||Reduced to the absurd||Proof by contradiction. The proof assumes the opposite of what must be proved, then shows this to be impossible, which proves the original statement. Proposition 6 uses Reductio ad absurdum.|
There are various words that I have used in this website which are not used by Euclid. They are in general use, and they make understanding the ideas easier.
|180°||The angle which makes a straight line.||Two right angles|
|Congruent triangles||Both triangles have all corresponding sides and angles equal.||The two triangles are equal.|
|Opposite angles||When two straight lines cross, the pair of angles which oppose each other||Vertical angles|
© Jo Edkins 2010 - Return to Euclid index