共50条信息
在正方体\(ABCD-A_{1}B_{1}C_{1}D_{1}\)中,\(E\)、\(F\)、\(G\)、\(H\)分别是\(BC\)、\(CC_{1}\)、\(C_{1}D_{1}\)、\(A_{1}A\)的中点.
求证:\((1)BF/\!/HD_{1}\);
\((2)EG/\!/\)平面\(BB_{1}D_{1}\)D.
如图所示,正方体\(ABCD-A_{1}B_{1}C_{1}D_{1}\)的棱长为\(a\),点\(P\)是棱\(AD\)上一点,且\(AP= \dfrac{a}{3}\),过\(B_{1}\)、\(D_{1}\)、\(P\)的平面交底面\(ABCD\)于\(PQ\),\(Q\)在直线\(CD\)上,则\(PQ=\)__________.
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