As shown in the figure, in △ ABC, ab = AC, and points D, e and F are the midpoint of △ ABC

As shown in the figure, in △ ABC, ab = AC, and points D, e and F are the midpoint of △ ABC

It is proved that: ∵ D, e and F are the midpoint of △ ABC, respectively, ∵ de ∥ 12ac, EF ∥ 12ab, and ∵ quadrilateral ADEF is parallelogram