Question

已知△ABC,分别以AB、AC为边向形外作等边△ABF、△ACE,再以AF、AE为边作平行四边形AEDF.证：△BCD是

Answer 1

在平行四边形AEDF中,有：AE = FD ；所以,AC = AE = FD .若∠ABC ＞ 60°,则有：∠ABC = 60°+∠ABD = ∠FBD ；若∠ABC ＜ 60°,则有：∠ABC = 60°-∠ABD = ∠FBD ；所以,∠ABC = ∠FBD .在△ABC和△FBD中,AB = FB ,...