Solution :
Given :In ∆ABC, XY ∥ AC.
XY divides ∆ABC into two points of equal area.
In ∆ABC, ∆XBY
∠B = ∠
∠ = ∠X
∠C = ∠
[∵ XY ∥ AC; (∠A, ∠X) and ∠C, ∠Y are the pairs of corresponding angles]
Thus ∆ABC ∼ ∆XBY by A.A.A similarity condition.
[∵ The ratio of areas of two similar triangles is equal to the ratio of squares of their corresponding sides]
[Given, ∆BXY = ∆BAC]
[∴ ∆ABC = 2. ∆XBY]