It is known that in △ ABC, ab = AC, the straight line DF intersects AB at point D, BC at point E, and the extension line of AC intersects at point F, BD = CF

It is known that in △ ABC, ab = AC, the straight line DF intersects AB at point D, BC at point E, and the extension line of AC intersects at point F, BD = CF

It is proved that the intersection of DG ∥ AC with BC is at g. ∵ DG ∥ AC, ∵ DGB = ∵ ACB, ∵ AB = AC, ∵ B = ∵ ACB, ∵ BD = DG, ∵ DGE = ∵ ECF, and ∵ BD = CF, ∵ DG = cf. in △ dge and △ FCE, ≌ DGE = ≌ ECF ∵ DEG = ≌ cefdg = CF, ≌ DGE ≌ FCE (AAS)