H
E
E
L
E
M
E
N
T
S
But AB is also equal to DE; therefore
the two sides AB, BC are equal to the two sides DE, EF respectively, and the angle ABC is equal to the angle DEF;
therefore
the base AC is equal to the base DF, and the remaining angle BAC is equal to the remaining angle EDF. [I.4]
Being what it was required to prove.
