BOOK I. PROP. XXXVI. THEOR.
37
ARALLELOGRAMS (
and
) on equal bases, and between the same parallels, are equal.
Draw
and
,
=
=
, by (pr. 34, and hyp.);
∴
= and ||
;
∴
= and ||
(pr. 33.)
And therefore
is a parallelogram:
but
=
=
(pr. 35.)
∴
=
(ax. 1.).
Q. E. D.