延长AG交BC于D,延长AI交BC于E
则 AG = 2GD
AE是角平分线
∴ AC/CE = AB/BE
可求得 CE = 2
连CI,CI也是角平分线
∴ AI/IE = AC/CE = 4/2 = 2 = AG/GD
∴ IG // ED
∴ IG / ED = AG / AD = 2/3
ED = CD - CE = 1/2
∴ IG = 1/3
延长AG交BC于D,延长AI交BC于E
则 AG = 2GD
AE是角平分线
∴ AC/CE = AB/BE
可求得 CE = 2
连CI,CI也是角平分线
∴ AI/IE = AC/CE = 4/2 = 2 = AG/GD
∴ IG // ED
∴ IG / ED = AG / AD = 2/3
ED = CD - CE = 1/2
∴ IG = 1/3