The given figure shows a pentagon ABCDE in which EG, drawn parallel to DA, meets BA produced at G and CF drawn parallel to DB meets AB produced at F.
Show that ar(pentagon ABCDE) = ar(∆DGF).
Given: EG||DA, CF||DB
Here, in Quadrilateral ADEG
Area (Δ AED) = Area (Δ ADG) –1
In Quadrilateral CFBD
Area (Δ CBD) = Area (Δ BCF) –2
Add –1 and –2
Area (Δ AED) + Area (Δ CBD) = Area (Δ ADG) + Area (Δ BCF) –3
Add Area (Δ ABD) to –3
Area (Δ AED) + Area (Δ CBD) + Area (Δ ABD) = Area (Δ ADG) + Area (Δ BCF) + Area (Δ ABD)
Area (pentagon ABCDE) = Area (∆DGF)