共50条信息
已知直线\(m\),\(n\),平面\(α\),\(β\),给出下列命题:
\(①\)若\(m⊥α\),\(m⊥β\),则\(α⊥β\);
\(②\)若\(m/\!/α\),\(m/\!/β\),则\(α/\!/β\);
\(③\)若\(m⊥α\),\(m/\!/β\),则\(α⊥β\);
\(④\)若异面直线\(m\),\(n\)互相垂直,则存在过\(m\)的平面与\(n\)垂直.
其中正确的命题是\((\) \()\)
已知直棱柱\({ABC}{-}A_{1}B_{1}C_{1}{,}{∠}{ACB}{=}60^{{∘}}{,}{AC}{=}{BC}{=}4{,}AA_{1}{=}6{,}E\)、\(F\)分别是棱\(CC_{1}\)、\(AB\)的中点.
如图所示,四边形\(ABCD\)与四边形\(ADEF\)都为平行四边形,\(M\),\(N\),\(G\)分别是\(AB\),\(AD\),\(EF\)的中点\(.\)求证:
\((2)\)平面\(BDE/\!/\)平面\(MNG\).
如图,在三棱柱\(ABC-A\)\(1\)\(B\)\(1\)\(C\)\(1\)中,\(E\),\(F\),\(G\),\(H\)分别是\(AB\),\(AC\),\(A\)\(1\)\(B\)\(1\),\(A\)\(1\)\(C\)\(1\)的中点,,若\(D_{1}\),\(D\)分别为\(B_{1}C_{1}\),\(BC\)的中点,求证:平面\(A_{1}BD_{1}/\!/\)平面\(AC_{1}\)D.
已知\(\alpha \)、\(\beta \)是两个不同的平面,给出下列四个条件:\(①\)存在一条直线\(a\),\(a\bot \alpha \),\(a\bot \beta \);\(②\)存在一个平面\(\gamma \),\(\gamma \bot \alpha \),\(\gamma \bot \beta \);\(③\)存在两条平行直线\(a\)、\(b\),\(a\subset \alpha \),\(b\subset \beta \),\(a/\!/\beta \),\(b/\!/\alpha \);\(④\)存在两条异面直线\(a\)、\(b\),\(a\subset \alpha \),\(b\subset \beta \),\(a/\!/\beta \),\(b/\!/\alpha \),可以推出\(\alpha /\!/\beta \)的是\((\) \()\)
在下列条件下,可判断平面\(α\)与平面\(β\)平行的是 ( )
如图,在多面体\(ABCDEF\)中,\(ABCD\)是正方形,\(BF⊥\)平面\(ABCD\),\(DE⊥\)平面\(ABCD\),\(BF=DE\),点\(M\)为棱\(AE\)的中点.
\((\)Ⅰ\()\)求证:平面\(BDM/\!/\)平面\(EFC\);
\((\)Ⅱ\()\)若\(AB=1\),\(BF=2\),求三棱锥\(A-CEF\)的体积.
如图,在正方体\(ABCD—A_{1}B_{1}C_{1}D_{1}\)中,\(E\),\(F\),\(G\)分别是\(AB\)、\(AD\)、\(C_{1}D_{1}\)的中点.
\((1)\)异面直线\(D_{1}C_{1}\)与\(DB\)所成角:
\((2)\)求证:平面\(D_{1}EF/\!/\)平面\(BDG\).
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