For, since the angle BAC is greater than the angle EDF, let there be constructed, on the straight line DE, and at the point D on it, the angle EDG equal to the angle BAC; [I. 23]
Probatio huius: Et quia angulus BAG angulo EDZ maior existit, statuam super lineam DE in puncto ipsius D angulum duarum rectarum linearum angulo BAG duarum rectarum linearum equalem, sitque angulus ille EDH,
Ad lineam enim D E, ad eiusque punctum D, constituatur angulus E D G, æqualis angulo A; (cadetque recta D G, extra triangulum D E F, cum angulus E D F, minor ponatur angulo A)
Title
Book I
