我给你讲你自己解C与点A重合则AE=CE∵CE+ED=DC=4∴AE+ED=4(设ED为x则AE=4-x)用勾股定理AE*2=ED*2+AD*2同理C点
△AOF为直角三角形,AO=2.5,OF=2.5÷4×3=15/8EF=2×OF=15/4
AC^2=AD^2+DC^2=3^2+4^2=25==>AC=5AD^2+DE^2=CE^2,CE+DE=4==>3^2+DE^2=(4-DE)^2==>9+DE^2=14-8DE+DE^2==>DE=5/8CE=4-(5/8)=33/8(EF/2)^2=CE^2-(AC/2)^2=(27/8)^2-(5/2)^2=(329/64)^2==>EF/2=329/64==>EF=329/32=10(9/32)