If a parallelogram has the same base as a triangle, and is between the same parallels, then the parallelogram is double (the area) of the triangle. * For let parallelogram $ABCD$ have the same base $BC$ as triangle $EBC$, and let it be between the same parallels, $BC$ and $AE$. * I say that parallelogram $ABCD$ is double (the area) of triangle $BEC$.
If a parallelogram (\(\boxdot{ABCD}\)) and a triangle (\(\triangle{EBC}\)) stand on the same base (\(\overline{BC}\)) and between the same parallels (\(\overline{AE}\), \(\overline{BC}\)), then the parallelogram is double the area of the triangle.
Proofs: 1