此题应用了三角形角平分线定理三角形ABC中,AD是角平分线,则BD:CD=AB:CD由题意得:CD:BD=4:6=2:3CD=2设EF交AC于G则AEGD是菱形GD=ED CG:GD=DE:EB 设CG=XX:4-X=4-X:6-(4-X)X=1.6即AG=2.4 CG=1.6EF是角AFC的角平分线 AF=DFAF:FC=AG:CG 设AF=FD=XX:X-2=2.4:1.6=3:22X=3X-6X=6即AF=6