H
E
E
L
E
M
E
N
T
S
GO be made equal to KL, and GP equal to LM;
and
let the parallelogram OGPQ be completed;
therefore
it is equal and similar to KM.
Therefore
GQ is also similar to GB; [VI.21]
therefore
GQ is about the same diameter with GB. [VI.26]
Let
GQB be their diameter, and let the figure be described..
