共50条信息
如图,在长方体\(ABCD—A_{1}B_{1}C_{1}D_{1}\)中,\(AD=AA_{1}=1\),\(AB=2\),点\(E\)在棱\(AB\)上.
\((\)Ⅰ\()\)求异面直线\(D_{1}E\)与\(A_{1}D\)所成的角;
\((\)Ⅱ\()\)若平面\(D_{1}EC\)与平面\(ECD\)的夹角大小为\(45^{\circ}\),求点\(B\)到平面\(D_{1}EC\)的距离.
如图所示,四边形\(ABCD\)为菱形,且\(∠ABC=120^{\circ}\),\(AB=2\),\(BE/\!/DF\),且\(BE=DF=√3\),\(DF⊥\)平面\(ABCD\).
\((1)\)求证:平面\(ABE⊥\)平面\(ABCD\);
\((2)\)求平面\(AEF\)与平面\(ABE\)所成锐二面角的正弦值.
如图,\(PA⊥\)面\(ABC\),\(AB⊥BC\),\(AB=PA=2BC=2\),\(M\)为\(PB\)的中点.
\((\)Ⅰ\()\)求证:\(AM⊥\)平面\(PBC\);
\((\)Ⅱ\()\)求二面角\(A-PC-B\)的余弦值;
\((\)Ⅲ\()\)在线段\(PC\)上是否存在点\(D\),使得\(BD⊥AC\),若存在,求出\(\dfrac{PD}{PC}\)的值,若不存在,说明理由.
四棱锥\(P-ABCD\)中,底面\(ABCD\)为矩形,\(AB=2\),\(BC= \sqrt{2} . PA=PB\),侧面\(PAB⊥\)底面\(ABCD\).
\((2)\) 设\(BD\)与平面\(PAD\)所成的角为\(45\)\({\,\!}^{○}\),求二面角\(B-PC-D\)的余弦值.
如图,正三角形\(ABC\)所在平面与梯形\(BCDE\)所在平面垂直,\(BE/\!/CD\),\(BE=2CD=4\),\(BE⊥BC\),\(F\)为棱\(AB\)的中点.
\((\)Ⅰ\()\)求证:直线\(DF/\!/\)平面\(ABC\);
\((\)Ⅱ\()\)若异面直线\(BE\)与\(AD\)所成角为\(45^{\circ}\),求二面角\(B-CF-D\)的余弦值.
如图,四边形\(ABCD\)与\(BDEF\)均为菱形,\(∠DAB=∠DBF = 60^{\circ}\),且\(FA=FC\).
\((1)\)求证:\(AC⊥\)平面\(BDEF\);
\((2)\)求二面角\(A-FC-B\)的余弦值\(.\)
如图,已知矩形\(ABCD\)中,\(AB=2\sqrt{2}\),\(O\)为\(CD\)的中点, 且\(AO\bot BO\),沿\(AO\)将三角形\(AOD\)折起,使\(DB=\sqrt{6}\).
\((\)Ⅰ\()\)求证:平面\(AOD\bot \)平面\(ABCO\);
\((\)Ⅱ\()\)求直线\(BC\)与平面\(ABD\)所成角的正弦值.
如图所示几何体为正方体\(ABCD-A_{1}B_{1}C_{1}D_{1}\)截去三棱锥\(B_{1}-A_{1}BC_{1}\)后所得,点\(M\)为\(A_{1}C_{1}\)的中点.
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