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高二数学,求解答,急求,求过程,谢谢
2个回答
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(1) 补齐长羡悄方体PB'C'D'-ABCD
PB=√(PA²+AB²)=√7
BC'=√(BC²+PA²)=√5
PC'=√(AB²+BC²)=2
BC'²=PB²+PC'兄棚渣²-2PB·PC'和携cosα
cosα=3√7/14
(2) S△EAD=PA·AD/2=1
VB-EAD=1/3·S△EAD·AB=√3/3
PB=√(PA²+AB²)=√7
BC'=√(BC²+PA²)=√5
PC'=√(AB²+BC²)=2
BC'²=PB²+PC'兄棚渣²-2PB·PC'和携cosα
cosα=3√7/14
(2) S△EAD=PA·AD/2=1
VB-EAD=1/3·S△EAD·AB=√3/3
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