共50条信息
如图,在四棱锥\(P-ABCD\)中,侧面\(PAD⊥\)底面\(ABCD\),底面\(ABCD\)是平行四边形,\(∠ABC=45^{\circ}\),\(AD=AP=2\),\(AB=DP=2\sqrt{2}\),\(E\)为\(CD\)的中点,点\(F\)在线段\(PB\)上.
\((1)\)求证:\(AD⊥PC\);
\((2)\)当三棱锥\(B-EFC\)的体积等于四棱锥\(P-ABCD\)体积的\(\dfrac{1}{6}\)时,求\(\dfrac{PF}{PB}\)的值.
在如图所示的几何体中,四边形\(ABCD\)是等腰梯形,\(AB/\!/CD\),\(AD=BC\),\(CB=CD=CF=1\),\(AB=2\),\(FC\bot \)平面\(ABCD\),\(AE\bot BD\).
\((1)\)求证:\(BD\bot \)平面\(AED\);
\((2)\)求二面角\(F-BD-C\)的余弦值.
在如图所示的多面体中,四边形\(ABCD\)是平行四边形,四边形\(BDEF\)是矩形.
\((2)\)若\(AD⊥DE\),\(AD=DE=1\),\(AB=2\),\(∠BAD=60^{\circ}\),求三棱锥\(F-AEC\)的体积.
已知四棱锥\(P-ABCD\),底面\(ABCD\)为菱形,\(PD=PB,\,\,H\)为\(PC\)上的点,过\(AH\)的平面分别交\(PB,\,PD\)于点\(M,\,N\),且\(BD/\!/\)平面\(AMHN\).
\((1)\)证明:\(MN\bot PC\);
\((2)\)当\(H\)为\(PC\)的中点,\(PA=PC=\sqrt{3}AB\),\(PA\)与平面\(ABCD\)所成的角为\(60{}^\circ \),求二面角\(P-AM-N\)的余弦值.
如图,在斜三棱柱\(ABC-A_{1}B_{1}C_{1}\)中,若\(∠BAC=90^{\circ}\),\(BC_{1}⊥AC\),则点\(C_{1}\)在底面\(ABC\)上的射影\(H\)必在直线________上.
如图,过底面是矩形的四棱锥\(F-ABCD\)的顶点\(F\)作\(EF/\!/AB\),使\(AB=2EF\),且平面\(ABFE⊥\)平面\(ABCD\),若点\(G\)在\(CD\)上且满足\(DG=GC\).
\((1)\)求证;\(FG/\!/\)平面\(AED\);
\((2)\)求证:平面\(DAF⊥\)平面\(BAF\).
如图所示,在四棱锥\(P-ABCD\)中,\(AB⊥\)平面\(PAD\),\(AB/\!/CD\),\(PD=AD\),\(E\)是\(PB\)的中点,\(F\)是\(DC\)上的点,且\(DF= \dfrac{1}{2}AB\),\(PH\)为\(\triangle PAD\)中\(AD\)边上的高.
求证:\((1)PH⊥\)平面\(ABCD\);
\((2)EF⊥\)平面\(PAB\).
如图所示,四棱锥\(P—ABCD\)的底面是矩形,\(PA⊥\)平面\(ABCD\),\(E\)、\(F\)分别是\(AB\)、\(PD\)的中点,又二面角\(P—CD—B\)为\(45^{\circ}\).
\((1)\)求证:\(AF/\!/\)平面\(PEC\);
\((2)\)求证:平面\(PEC⊥\)平面\(PCD\);
\((3)\)设\(AD=2\),\(CD=2\sqrt{2}\),求点\(A\)到平面\(PEC\)的距离.
\((\)Ⅰ\()\)求直线\(AC\)与\(PB\)所成角的余弦值;
\((\)Ⅱ\()\)在侧面\(PAB\)内找一点\(N\),使\(NE\bot \)面\(PAC\),并求出点\(N\)到\(AB\)和\(AP\)的距离.
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