共50条信息
如图,在四棱锥\(P-ABCD \)中,\(PA⊥ \)底面\(ABCD\),\(AD⊥AB \),\(AB/\!/DC,AD=DC=AP=2,AB=1 \),点\(E\)为棱\(PC\)的中点.
\((2)\)在线段\(BC\)上是否存在一点\(P\),使\(AP\bot DE\)?证明你的结论.
如图,三棱柱\(ABC-{{A}_{1}}{{B}_{1}}{{C}_{1}}\)中,\({{A}_{1}}C\bot \)底面\(ABC\),\(\angle ACB={120}{}^\circ \),\({{A}_{1}}C=AC=BC=2\),\(D\)为\(AB\)中点.
\(\left( {1} \right)\)求证:\(B{{C}_{1}}/\!/\)平面\({{A}_{1}}CD;\)
\(\left( {2} \right)\)求直线\({{A}_{1}}D\)与平面\({{A}_{1}}{{C}_{1}}B\)所成角的正弦值.
在平面四边形\(ABCD\)中,\(AB=BD=CD=1,AB\bot BD,CD\bot BD\) ,将\(\Delta ABD\)沿\(BD\)折起,使得平面\(ABD\bot \)平面\(BCD\),如图所示.
\((1)\)求证:\(AB\bot CD\);
\((2)\)若\(M\)为\(AD\)中点,求直线\(AD\)与平面\(MBC\)所成角的正弦值.
已知向量\( \overset{→}{AB} =(1,5,-2)\),\( \overset{→}{BC} =(3,1,2)\),\( \overset{→}{DE} =(x,-3,6).\)若\(DE/\!/\)平面\(ABC\),则\(x\)的值是\((\) \()\)
在正方体\(ABCD-{{A}_{1}}{{B}_{1}}{{C}_{1}}{{D}_{1}}\)中,\(O\)是\(AC\)的中点,\(E\)是线段\({{D}_{1}}O\)上一点,且\({{D}_{1}}E=\lambda EO\).
\((1)\)若\(\lambda =1\),求异面直线\(DE\)与\(C{{D}_{1}}\)所成角的余弦值;
\((2)\)若平面\(CDE\bot \)平面\(C{{D}_{1}}O\),求\(\lambda \)的值.
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