过A作AF垂直AC(F和B在AC的同侧),截取AF=AD,
连接CF,CF与AB的交点为G(E点),G(E点)点即为所求.
连接DE(G),DE=FE
CE+ED=CE+EF=CF
CF=(1^2+3^2)^(1/2)=10^(1/2)