In a Δ ABC, if L and M are points on AB and AC respectively such that LM||BC. Prove that:
(i) ar(Δ LCM) = ar(Δ LBM)
(ii) ar(Δ LBC) = ar(Δ MBC)
(iii) ar(Δ ABM) = ar(Δ ACL)
(iv) ar(Δ LOB) = ar(Δ MOC)
(i) Clearly, triangles LMB and LMC are on the same base LM and between the same parallels LM and BC.
Therefore,
Area ( = Area () (1)
(ii) We observe that triangles LBC and MBC are on the same base BC and between the same parallels LM and BC.
Therefore,
Area (ΔLBC) = Area (ΔMBC) (2)
(iii) We have,
Area ( = Area ( [From (i)]
Area ( + Area ( = Area ( + Area (
Area ( = Area (
(iv) We have,
Area ( = Area ( [From (ii)]
Area (LBC) - Area ( = Area ( - Area (
Area ( = Area ()