Question

在三角形ABC中,D为AC上一点且AD等于BD等于BC,则角ABD等于多少

Answer 1

设∠ABD = X .（按题中的条件无法确定∠ABD,还要加个条件：AB=AC）

已知,AD = BD = BC ,可得：∠BAD = ∠ABD = X ；

已知,AB = AC ,BD = BC ,可得：∠ABC = ∠BCD = ∠BDC = ∠BAD+∠ABD = 2X ；

因为,∠BAD+∠ABC+∠BCD = 5X = 180° ,

所以,X = 36° ,即有：∠ABD = 36° .