H
E
E
L
E
M
E
N
T
S
let MF be to NH as KAB is to LCD;
I say also that,
as AB is to CD, so is EF to GH.
For,
if EF is not to GH as AB to CD,
let EF be to QR as AB to CD [VI.12]
and
on QR let the rectilineal figure SR be described similar and similarly situated to either of the two MF, NH. [VI.18]
