Proposition 36
Theorem
Two parallelograms (◇ABCD , ◇EFGH ) on equal bases (ᅵBCᅵ = ᅵFGᅵ ) and between the same parallels (BG ‖ AH ) have the same area.
τὰ παραλληλόγραμμα τὰ ἐπὶ ἴσων βάσϵων ὄντα καὶ ἐν ταῖς αὐταῖς παραλλήλοις ἴσα ἀλλήλοις ἐστίν.
Parallelograms which are on equal bases and in the same parallels are equal to one another.