u3cfh
幼苗
共回答了14个问题采纳率:92.9% 举报
延长CD到E,使CE=AC
∠ACD=60,AC=CE==>△ACE为等边三角形
==>∠EAC=60,AE=AC=CE=AB
∠1=(180-∠BAC)/2-∠ACD=30-∠BAC/2
∠ACD=∠ABD=60==>A.C.B.D共圆
==>∠1=∠2
∠3=∠EAC-∠BAC-∠2=60-∠BAC-(30-∠BAC/2)=30-∠BAC/2
==>∠2=∠3
AD=AD
==>△AED≌△ABD
==>ED=BD
==>BD+DC=ED+DC=CE=AB
1年前
追问
2