如图所示,大正方形ABCD内有一个小正方形DEFG,对角线DF长为6cm……
推荐回答（1个）
DB=DF+FB=DF+(D'B-FB)=6+(6-3)=9
2*AB*AB=DB*DB=9*9
大正方形面积=AB*AB=0.5*DB*DB=0.5*9*9
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