∵⊿BEM∽⊿CDM(A A)
∴BM:CM=BE:CD=1:2
S⊿BOD:S⊿COD=1:2
S⊿COD=2S⊿BCD /3
S⊿BCD=S平行四边形ABCD /2
S⊿COD=S平行四边形ABCD /3
S⊿BEM:S⊿CDM=(1:2)²=1:4
S⊿BEM:S平行四边形ABCD =1:12