连接OE(O为圆心)△ABO≌△AFO;△EFO≌△ECO设CE=x则在直角△ADE中(4+x)^2=4^2+(4-X)^2得x=1所以S=4*3/2=6
连接OF、AO、OE有OF⊥AE,AO⊥OE(可证)△AOF∽△FOE∽△AOE△AOF≌△AOB,△FOE≌△COEAF=AB=4 FO=2AO=2√5 EO=√5 AE=5 FE=EC=1所以DE=3 S△ADE=4X3/2=6
童鞋?等答案出来你还来得及交作业不?