34
BOOK I. PROP. XXXIII. THEOR.
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.
