H
E
E
L
E
M
E
N
T
S
let CE be drawn from the point C at right angles to AB, [I.11]
and
let it be made equal to either AC or CB; [I.3]
let
EA, EB be joined;
through E
let EF be drawn parallel to AD,
and through D
let FD be drawn parallel to CE. [I.31]
