In the Elements of Geometry there is no other use, as it seemeth of the gnomons than that in one word three parts of a parallelogramme might be signified and called by three letters aei. Otherwise gnomon is a perpendicular.
25. Parallelogrames of equall height are one to another as their bases are. 1 p vj.
As is apparent, by the [16 e iiij]. Because they be the double of Triangles, by the [12 e], of first figures: As ae, and ei.
Therefore
26 Parallelogrammes of equall height upon equall bases are equall. 35. 36 pj.
As is manifest in the same example.
27 If equiangle parallelogrammes be reciprocall in the shankes of the equall angle, they are equall: And contrariwise. 15 p vj.
It is a consectary drawne out of the [11 e vij]: As here thou seest: And yet indeed both that (as there was sayd) and this is rather a consectary of the [18 e iiij], which here also is more manifest.