giggsml
春芽
共回答了11个问题采纳率:72.7% 举报
∵∠CAF=∠BAF,∴CF/BF=AC/AB,[三角形内角平分线定理]
∴CF/(CF+BF)=AC/(AC+AB),[合比定理]
∴CF=BC×AC/(AC+AB).·········①
∵AC⊥BC,CD⊥AB,∴由射影定理,有:AC^2=AD×AB,∴AD=AC^2/AB.
由三角形内角平分线定理,有:CE/ED=AC/AD=AC/(AC^2/AB)=AB/AC.
∵EG∥DB,∴CE/ED=CG/GB,结合证得的CE/ED=AB/AC,得:CG/GB=AB/AC,
∴(CG+GB)/GB=(AB+AC)/AC,[合比定理]
∴GB=AC×BC/(AC+AB)·········②
比较①、②,得:CF=GB.
1年前
8