Problems: 4401–4410

[摘要] Let D and E be the centres of squares erected externally on the sides AB andAC, respectively, of an arbitrary triangle ABC, and de ne F and G to be theintersections of the line BC with lines perpendicular to ED at D and at E. Provethat the resulting segments BF and CG are congruent.

[学科分类] 数学（综合）