Euclid's
Elements
 Book 1: The 48 Propositions
| 41 |
If a
parallelogram has the same base with a triangle and be in the same parallels,
the parallelogram is double of the triangle. |
| For let the
parallelogram ABCD have the same base BC with the triangle EBC, and let it be
in the same parallels BC, AE. |
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