E、F应该在BC、AD上?由题知AC=2√5（㎝）∵四边形AECF是菱形∴EF⊥AC要求S四边形AECF,只需求EF的长度连接CF,设AC与EF相交于O在ΔCDE与ΔCOF中,由勾股定理得：OC^2+OF^2=CD^2+DF^2=(4-DF)^2∴DF=1.5,OF=½√5∴...