H
E
E
L
E
M
E
N
T
S
on the straight line EF, and at the points E, F on it
let there be constructed the angle FEG equal to the angle ABC,
and
the angle EFG equal to the angle ACB; [I.23]
therefore
the remaining angle at A is equal to the remaining angle at G. [I.32]
Therefore
the triangle ABC is equiangular with the triangle GEF.
