ศัพท์ทางคณิตศาสตร์
The ratios of given magnitudes to one another are given
Let A, B be two given magnitudes, the ratio of A to B is given.
Because A is a given magnitude, there may (1. def. Dat.) be found one equal to it; let this be C, and because B is given, one equal to it may be found; let it be D; and since A is equal to C, and B to D; therefore (7. 5.) A is to B, as C to D; and consequently the ratio of A to B is given, because the ratio of the given magnitudes C, D, which is the same with it, has ABC been found.