Editing Euclidean geometry (section)

===Pons asinorum===
The [[pons asinorum]] (''bridge of asses'') states that ''in isosceles triangles the angles at the base equal one another, and, if the equal straight lines are produced further, then the angles under the base equal one another''.<ref>Euclid, book I, proposition 5, tr. Heath, p.&nbsp;251.</ref> Its name may be attributed to its frequent role as the first real test in the ''Elements'' of the intelligence of the reader and as a bridge to the harder propositions that followed. It might also be so named because of the geometrical figure's resemblance to a steep bridge that only a sure-footed donkey could cross.<ref>Ignoring the alleged difficulty of Book I, Proposition 5, [[T. L. Heath|Sir Thomas L. Heath]] mentions another interpretation. This rests on the resemblance of the figure's lower straight lines to a steeply inclined bridge that could be crossed by an ass but not by a horse: "But there is another view (as I have learnt lately) which is more complimentary to the ass. It is that, the figure of the proposition being like that of a trestle bridge, with a ramp at each end which is more practicable the flatter the figure is drawn, the bridge is such that, while a horse could not surmount the ramp, an ass could; in other words, the term is meant to refer to the sure-footedness of the ass rather than to any want of intelligence on his part." (in "Excursis II", volume 1 of Heath's translation of ''The Thirteen Books of the Elements'').</ref>