共50条信息
如图,梯形\(ABCD\)中,\(AD= BC\),\(AB\parallel CD\),\(AC\bot BD\),平面\(BDFE\bot \)平面\(ABCD\),\(EF\parallel BD\),\(BE\bot BD\)
\((1)\)求证:平面\(AFC\bot \)平面\(BDFE;\)
\((2)\)若\(AB=2CD2\sqrt{2}\) ,\(BE = EF =2\),求\(BF\)与平面\(DFC\)所成角的正弦值.
如图,在长方体\(ABCD\)\(-\)\(A\)\({\,\!}_{1}\)\(B\)\({\,\!}_{1}\)\(C\)\({\,\!}_{1}\)\(D\)\({\,\!}_{1}\)中,\(AB\)\(=\)\(BC\)\(=2\),\(AA\)\({\,\!}_{1}=1\),则\(BC\)\({\,\!}_{1}\)与平面\(BB\)\({\,\!}_{1}\)\(D\)\({\,\!}_{1}\)\(D\)所成角的正弦值为\((\) \()\)
在正方体\(AC_{1}\)中,\(AB=2\),\(A_{1}C_{1}∩B_{1}D_{1}=E\),直线\(AC\)与直线\(DE\)所成的角为\(α\),直线\(DE\)与平面\(BCC_{1}B_{1}\)所成的角为\(β\),则\(\cos (α-β)=\)________.
已知边长为\(6\)的正方体\(ABCD-A_{1}B_{1}C_{1}D_{1}\),\(E\),\(F\)为\(AD\)、\(CD\)上靠近\(D\)的三等分点,\(H\)为\(BB_{1}\)上靠近\(B\)的三等分点,\(G\)是\(EF\)的中点.\((1)\)求\(A_{1}H\)与平面\(EFH\)所成角的正弦值;\((2)\)设点\(P\)在线段\(GH\)上,\( \dfrac {GP}{GH}=λ\),试确定\(λ\)的值,使得二面角\(P-C_{1}B_{1}-A_{1}\)的余弦值为\( \dfrac { \sqrt {10}}{10}\).
在棱长为 \(a\) 的正方体\(ABCD-{A}_{1}{B}_{1}{C}_{1}{D}_{1} \) 中,\(E\) 、 \(F\) 分别为\(D{D}_{1} \) 和\(B{B}_{1} \) 的中点.
\((\)Ⅰ\()\)求证:四边形\(AE{C}_{1}F \) 为平行四边形;
\((\)Ⅱ\()\)求直线\(A{A}_{1} \) 与平面\(AE{C}_{1}F \) 所成角的正弦值.
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