EQual Triangles standing on the same Base, are between the same Parallels.
If the Triangles ABC, DBC, which have the same Base BC, are equal; the Line AD drawn through the tops of those Triangles, shall be Parallel to the Base. For if AD, BC, are not Parallels; having drawn a Pa∣rallel through the Point A, the same shall fall either under AD, as AO; or above as AE. Let us suppose it falleth above, continue BD, untill it meets AE in the Point E; then draw the Line CE.