angle ACD=angle ABC+angle BAC(exterior angles are equal to sum of interior angle)
1/2 angle ACD=1/2 angle ABC+1/2 angle BAC
angleECD=angle EBC+1/2 angle BAC....(1)eq
ECD=EBC+BEC...(2)eq
from(1) and (2)
EBC+1/2BAC=EBC+BEC
1/2BAC=EBC-EBC+BEC
1/2BAC=BEC
ie angle BEC=1/2 angle BAC
