H
E
E
L
E
M
E
N
T
S
But
AB is also equal to DC; [I.34]
therefore
the two sides EA, AB are equal to the two sides FD, DC respectively,
and
the angle EAB is equal to the angle FDC, the interior to the exterior; [I.29]
therefore the base EB is equal to the base FC, and
the triangle EAB
will be equal to
the triangle FDC. [I.4]
