小学四年级数学辅导练习：ABDE的面积是多少
奥数网整理
2022-04-25 21:57:31
【答案】
四边形AFDC的面积=三角形AFD+三角形ADC
=(1/2×FD×AF)+(1/2×AC×CD)
=1/2(FE+ED)×AF+1/2(AB+BC)×CD
= (1/2×FE×AF+1/2×ED×AF)+(1/2×AB×CD+1/2×BC×CD)。所以阴影面积=四边形AFDC-三角形AFE-三角形BCD=(1/2×FE×AF+1/2×ED×AF)+(1/2×AB×CD+1/2×BC×CD)-1/2×FE×AF-1/2×BC×CD=1/2×ED×AF+1/2×AB×CD=1/2×8×7+1/2×3×12=28+18=46。
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