Theorem 14.1.1

Theorem: Parallelograms on the same base and lying between the same parallel lines are equal in area.

Given: Two parallelogram ABCD and ABEF with the same base $\overline{AB}$ and between the same parallel segments $\overline{AB}$ and $\overline{DE}$.

To Prove:

Parallelograms ABCD and ABEF are equal in areas,

i.e. $▰ ABCD = ▰ ABEF$.

Proof: