Page:First six books of the elements of Euclid 1847 Byrne.djvu/68

34 TRAIGHT lines ( and ) which join the adjacent extremities of two equal and parallel straight lines ( and ) are themselves equal and parallel.



Draw the diagonal.

= (hyp.) = (pr. 29.)

and common to the two triangles; ∴  =, and  =  (pr. 4.); and ∴ ||  (pr. 27.). Q. E. D.