Given:A pentagon ABCDE where BF∥AC
(i)△ACB and △ACF lie on the same base AC and are between the same parallels AC and BF.
∴area(△ACB)=area(△ACF) since triangles with same base and between the same parallels are equal in area.
(ii)Both AEDF and ABCDE have AEDC common.
In part (1), we proved that
area(△ACB)=area(△ACF)
Adding area(AEDC) both sides,
⇒ area(△ACB)+area(AEDC)=area(△ACF)+area(AEDC)
⇒Area(ABCDE)=Area(AEDF)
Hence proved.