Cho hình lập phương ABCD.A'B'C'D' cạnh a. Gọi M, N...
Câu hỏi: Cho hình lập phương ABCD.A'B'C'D' cạnh a. Gọi M, N lần lượt là trung điểm của AC và B'C' (tham khảo hình vẽ bên).
![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAATYAAAEMCAYAAABOXZpiAAAACXBIWXMAAA7EAAAOxAGVKw4bAAAdv0lEQVR4nO2dwW7qSrOFi6sdaeeRQGRAo5PByeP8oysbBmA/Uib7imYAsv83ypFyJN8BKdM2tjG4bVe31yehcwKEeNvNcnfV6qpZlmUZAQCAR/zP2AcAAAC2gbABALwDwgYA8A4IGwDAOyBsAADvgLABALwDwgYA8A4Im4Os1Zpms9nYhwGAWCBsjhHvY9JHPfZhACCaGXYeuIU5U8OlA6AazNgcIt7HYx8CAE6AGZsjpOeUFm+LwnO4dABUgxmbI4TbkNRKUXJK8ufSczriEQEgFwibA8TbS8Ig2AQ0X87z5z//fI54VADIBcLmAPqsSa0UqZUqPP/68jrSEQEgm19jHwBohu0dvAQtLD+/RzooAIQDYRNOuA2JiG4SB0RE9DLwwQDgCBA2wbCoRZuI6IXo6/uLXl9e8+e/vr/GPDwAxAJhE0p6Tinex5SckkLCgIhIHzXpo0ZWFDhLek4bd9ColboZ948AH5tQ1mpNREQHfbh5LdyGuVkXlw+4yFqtC8IW7SKi70uijJ+PNhEFu+C5P5ABUUS7KFMrlRFRplaq8XUiypJTMsJRAtCd379+145hHuPRLnrqszFjE0a5akd5KVp+Xa1U5awOAMmYO2nqJIjH+jMShRibMO5dRNyHgA/wcrPszSzwi4j+vYjgo/E2GHQdQB81zWYzWqs1EgbACdJzmo/Ze0mCWv69/OeZHTZYigqnavN7tItGOhoA2sGWJKYsM22Wma8vr/TPv/9QtIso2DyWRMBSVDhVd7vyoAHAJdLj/VVHek7pn3//ISJ6WNSIsBQVT900PtpFlGUZHniIe/z919+FsVpeburz/fha1yrREDbBcHwi2AT5IMiyjNRKUbgNEXMD4lirNf3z7z/5eE1OyU3WnnfMqOV9YXs67JIBkbCPhz0+0S7KzMuVnJLcy/as1wcAm/z919+597I8Xk3oF9W+lmXFsf0smLEJhHcdZFmWp7nLZYvmyzllWUbRLspnb2jyAsaCZ2r3PJXpOc2znXVwDLmLPxPCJoy6rVTz5bzyQgebgLIsy38Xy1MwNB/vH0TUToju+df4Bp3opNkKcgcImxDSc9q4P/QeB32gRCekj5oWbws0fgG9kx4vXrU2MzWiayVo8/fjfZzvfWZRO+gDzVfPb4AnIsTYJMAxhaq9oc9g7jXFXlLQB8kpyX7/+l07Zqtiwrw3tO5hM1aMGdvIsAG3zZ7PtjG0gz7ky9PF24LibYzlKbBGvI1p8bag//zvf1qvLubLOX19fzXaRJ7xq9ViTSLBw5Qzn000ZZmaQPYU2CQfs7p5zD47Xm2BGdtI5EHSikKSNuHsqel9Q/YUPIPVGFjPQNhGoMrO0TcHfcgbwqzVGskF8BDmmO2SrRwKCNvAdMl8doUtI4lOKNyGNJvNIHDgLmOO2WeBsA1EVztHVV/RZ5mvbpenSC6AMl3H7JiguscA6KOmtVp3qnZbZ9DtwkEf8qzs4m3RrcZ8B8JteGn+/E2k3pubeKTnlD7/fLZ+P3iOR7L1IhktbTERbHvU+oKzWGqlBs2emllbarE/sPxe+PTsY2PMjp0VhbD1SFNTlmc46IOVz2nCPOYh/l6WZVm0iVoJm9nERvqNwlUesSA1AWHzFFsDhBlyoAztfeN/W5OwlWd2mKnZx+aYHVvYkDzoAXMjr4vxnyrvW5/Z0za+unLVYBfPq2Q4SdC3r3IoIGyWKXjUhJsY72F63/rKnt7rCE5Euai64J9yETPz6YOoEUHYrOJqaryJ3Pt2MiqHbO3N3ljUsuza1MP8/PScUrgNC5VUow2a2djCxzFLBGGzwhB+H5s+tmcoLE/3/cze8n/fy/W5cBuSWl0sHXktr3fM3LrisketDRC2jpjt8focIH342J7hoA900IdC3bcue0/N3+Ua+FwTPz2m+d5EU0R9WS6NBV87Ij9FjQjC1gnnTYxPolaKsiyj5JR0Si5wfC1fZv7M1F5fXomIKNxfl6DYuG8HLujo/ZgdLR/rOJzOHtJ2MJSv7FGeLWwZbIKCJYB/5s8yX+OfUXrpedqWHLIB7B4OslZrCrfhoKlxvtNK5Ca50HL2xjOzqp+5pJP5MxEyo89SKJPleLa+DRC2BxmqjpprlL1vs9nsbvb0Znn5ff1fThgQFT1sOOePM0aZrLGBsD3AFAfIo3BZ8qbsKWfkWNjy11+Kn0N0mamav48qJI/hc+azkdEWwY6hVmrU/Yljxyye4aAPlVuzzD2fVNr3Ge2iPAZk/n7Ve0E9ySkZdcyOPV7d+qaMwNgDpHwcLmImF6JdlJ9P7PfsBwkVZSBsgkn0+APEF6rKE7k2A3UBCaKWZeMLG2JsNaTnlBZqeh61vpgv54UsJ4OYmT3i/aUtXnJKJj9mIWwVrNWaFm+L3GUP7DBfzm/sGuE2pPQIcevKGBYkyUDYSph2DmmeKR9mN+Y5jXbRxfumFjfZT9AeWJBugbAZSC7fwssMX0hOCQWbgLIso4M+ULgNHzL3gguwIFUDYfvBFDVpMzUfMb+EvPcUXbMeY7IetRZA2AgDZEiCTUCJvk0iEN1uzSpXzQUX0qPfJYdsMGlh870mlVSa9iry1qxoF1G8j9HUuQRn64kwZpuYrLANVUfNFmMXmhwajr8VlqcTz57G23iSZbKeYjQH3YiYPTTBcLB59NnfowmXLbLd9axvxjboTq4TPFLj4/H55/Op3+PlKXu19FGTWikKNsN3rR8DHrMSs/VSmdRS1HVRcz1TWK6/9ihcOYSov65Z0jDtHFMKRXRlMsLmut/HBx+brSznVLKnSGw9zySEDQNEDmYbvS6YhS25urBP2VOM2W54H2PDAJFDZvQOtcVBHyg9phTuw3zmppbK2fLX3EeVCGO2C97O2NJzSrPZjIgwQHxnvro2dQ63Yb731DVcsyBJxkth49iLT36fqfnYnqHcd8Gl5AJKDllmNKNJT4zRFg/cp9xOr2/K3jfJ48E1j1obxvaxeSVsQ/ZNBO2JNpdBHmyC4f/2zxdsrL9/Dx9FLcvGFzZvlqJT6JvoyrLqhp/uUx/vH4P/aXNrFmdPpZxH1y1IkvFC2KYwQFz2sX19fxHRuD1BD/pAiX68qXNfIFvfL84LGwaIfD7eP0QkPuar2+TC0AKHijLD4KywYYC4w3w5F3WNyluz4u0wZcl5tsjHAPrDSWGD3wfYIPe+7fsvS843Yp8sSJJxTthY1DBA3MB00kukyvtm+3i5n0Oi4VEbilmW9bDP5Yd7d8BHy87E+xgtxhyDr1mPw8wqnF2PdhGpleo8zlyvKPMsY1/3XveK6qMmfdT5z8EmoNeX1/z5R0RqqgMEDAvvPeXy29Euerrum5mtB8PS64yNiPL9muU/Y8bJ7h0CkgTuUnf9XYBvpmqlKNpFD91Qpz5mx56x9Rpji7eXpWjVHa/tIJn6AGHSc5qfT1fg45Vg9XgGM3u6eFu0Pv8Ys+PTb/Lgx3FeVTn1XvwNdo4i+qgp3MsNwlcR7AKKdpG1GmxjYWZPm7xvbcZsek7F7HzwmV5jbJxdKs/Y0mOax96SU1J4/+vLK9E3kT5fXoeouY0vfQmq+i7Ml/N8vNLLZfzWZevjfVyIOXPPBrVSFG9jCnZ+nCcp9CZsdXcl8wKbiYB4H9/cCbm3JKD8C4HzMS68rC4nxoiqEw1mLJk73hNdlqvsa9NHDWGzTV+768tVFaJdlFcyoIpqBuZreODh4iPaRJVjuq7NI1c9IfKqyE6WZROo7sExlmAT5MFYtVK0eFsUZnXlAHNySii7lFXC46czOt/xXXnwdR37OPp6lMesOevilUmjkfyleuwDC2Q9QQ13oro7Feqp+cNUCn5W1VNL9LXIZdO/P9gElTM9H/ByxnY36/NS/TTfuXytpzZFfDdT52PW+Hdy9vrezgWueoL4mn16ETbu+B1tqtP8ZmaowHcfR+MHLvrYpkh6vmb868Y/I63qiU/0ImzsW1Pvt7GDwoUv+5tqZnLAPR9bsAkKVp6pYGZKsfIYD+t2D95KQXSZuemjzn0+X99fuV2has8nV1oFfuD7MrSKsgUEjINVYTNFjX8u05QlqtqhAIBL1K5GKkjP6STFfwisLkW5cUbTozGmgBibF4TbMN/8DqpxuYeFC8gqNIkYmxdMeebddl8s77wB/SBK2BBjq4dnwy4guWLuUDSdA94oj2Vof4gStinf6X2BPYxTddPzxnYiuulhioo1wyFK2BBjq8c1H5vrpYq6cNCHfHP74m2R91JAr47h6LVs0cMgxlYL+9iku9S5vM/UYfFiZ8CjFXhBN0QJG2JswDd8qUfnGqKWooixAQBsIErYEGNzm/SY0mw2Q1YUjI4sYUOMzWm4nDtm3mBsRAkbYmz1uOBj4+uHuBIYG1HChju92+D6ASmIEjbE2NxGLdVkjblAFrKEDTG2RqT3o5yvUDgRyECUsCHGVg+qQQDQHlHChhiNu6TnFD1PgRhECRtibO6ijxr+NSAGWcKGGJuzQNSAJEQJG2Js9aiV3Ixjepx2qSIgD1HChhhbPZJbtfGOAwgbkIIoYUOMzU3myzlFuwg7DoAYZAkbYmyNSPWxqZWCqAFRiBI2xNjqgY8NgPaIEjbE2Nwk3sdiZ5NgmogSNsTY3IObZKMDOpCELGFDjM1ZEGMDkhAlbIix1SPZxwaANEQJG2Js9Uj2sQEgDVHChhibe7hQ2RdMD1nChhhbI8g8AtAOUcKGGFs98LEB0B5RwoYYm1vE+5hms9nYhwHADaKEDTE2t4B3DUhFlrAhxuYM6TmFsAGxiBI2xNjqkeZjY1GLdtHIRwLALaKEDTG2eqT62LDjAEhElLAhxuYO8K8BycgSNsTYAAAWECVsiLE1g2A9AO0QJWyIsdUT72Naq/XYh0FEV/8a+ogCqYgSNsTY3IBn1kgcAKnIEjbE2JwAM2sgHVHChhibGyDWB6Tza+wDMMFMoB5JBl1JxwJAFaKEDTG2eiQZdBFbA9IRtRRFjA0AYANRwoYYWzMSYlvpOaV4C5sHkI0oYUOMrR4pPrZwG1K4D8c+DAAaESVsiLHJJj2iVBFwA1nChhibaPQZpYqAG4gSNsTYZIMdB8AVRNk9EGOrR4J37OP9A9cIOIEoYUOMrR4JPrb5ck7z5XzUYwCgDaKWooixAQBsIErYEGNrZsyMZHpOKdzC5gHcQJSwIX5Tz9g+Nn3UqL8GnEGUsCHGBgCwgSxhQ4xNLDDmApcQJWyIsclFH/XodhMA2iLK7oEYWz1j+9jQag+4hKgZG2Js9UjwsQHgCrKEDTE2AIAFRAkbYmwyibcySiYB0BbE2BwiPaejbGlC/TXgGqJmbIix1RPvY1q8LUb5u0QoVQTcQpawIcYmFpQqAi4hStimEGOL9zHNZrPG96THlGazGfZmAvAkooRtCjG2NmLFMS0J5yPYBPCwAecQJWy+x9jM7k7pOa19H29fwvIPgOeQJWyex9jM7GLd3ss6wRtr5tQkwABIRZSw+RxjW6t1qy1RLHgSspDhNhwlEwtAV+BjG4D0fGlbl2UZxfu4VZytvAzlzxhyeerr9QDjc6+2X904X6t1/l1qQpSw+RpjC7chJaek02foo6ZwGw4qbChVBPqAxzKTF3j4voZr9FFTtIlovprf/G4bRC1FfYyx8Z2p7Y4BtVKdRdAWEDbQB2ql8lBLtIvooA8UbAIKdpc4cnJKSB81LVQxDPJIBWdRwuZjjC3chqSW7csNSeoEFWwCMSIL/IJvmlVx5/lynj9vJq9YH6LN/fizKGHzLabDd5hwH9JsNiuYbh8x35qNVIbMUka7SIzIAjdZq3XlmGVhqxtfLGzmqoH1IdjdD8cgxtYj4TakaBcV4mIc/GxLek4LmcnF24KCTXC5yN9E6l0VBke8j+nr+6v2dT4ufp1einfIqte/vr/ypUN6Tunzz2ft60SXwZie08Lrry+v+Xno+jofh/6jC6/T93XQ33ud6LLDQ5914XV6uQau773Ox8rnver1e+er6+uSzme8jfPX+aauj5oWb4tCsP+Rm3ohrvyIPmSCiHZRJuyQnibaRVm0iyqfJ6LW/07z/VUPtVL5e5NT0vh6m/dUvW4ea93xtDlmW69L+Qxf/kafx9n0t6q+H+X3mGPz96/fWaKT2t8xEaUiwSbwQtgSndT+O0zhaINaqUah6gu1UoP9LZfx6WbchSZhK48jHtMHfaj9PP5dU/yCTdD6eERdER8GSdOMLDklBaFqumNl2XUARLsoS05Jlpza3a26wuJ77/iAH2O2LbwKaRq/5g2xbsz+/vW78ZyZN/+2M7Qyoq5ItHF7kPBMre6ilGdfRNQoVtEmGkzMTHyZOQ+Bj8J20IeLiG2uwlWekVWNyzaz/DahGB5/Xc6rrOSB4z62+Wre6Ih+tBlLm+xPH/iWnQbtyLP4RnCfx2CwCRrN4Vw6vu0Yb9oymP73kkXtYjUSZffw0cf2CPqoRfQWUEslYq8q6I/y1j62FPFz0S5qVXQhPad5fcE2otbkX+Pj0v936WHbyWr09FyvB3yc1relKgsE5OPSmE1Oyc2SsuvnPTpmm/6uze+ArKWoZz62toTbkOJ9TGql0DsUWIF9Z6aPMdyGheoxXfYd84yv7Zg1Teb8+6avjos8WPsOdJZGi7h097OJJGsF39VBOySNWb52j2Ten0H9pe4mvm5+pyJxZj7USllNlImasU01xiZpljZGFRHwOOaOBL5Wn38+8wSAWikKNkGrGoCPwDtnklPyUAxs6DEuKnkwlWxcek4fqlQAABPvL82rF2+LS6Dd2J7HAf8sy+igD2JEbQxEzdimEGPjWIM+alJLdVNvamzQGUsG5t5Mc+8qXx+1UpX1yvqCs/WZI419ZAmb4z62e5gb2iXe9bgKA6we48GzMHMmxsJ2zyfZB2bQX1LI5B6ihM33GBsPEKl3vfly+C/OVDFjZObMvWCO3QSj3mTYV+litl6UsPkeY3NtcAD7sK3BFLBod11SSrmxPGrnkIYoYfMxxhbv45t6Z2AacH0y8/qbohZtotG2zTXBSQJXRY2IhBhwfpDkCbKBWZ3DBdRKOXOsUqgas2V3vxSPYht4zI5RfMEmouwevsTY0mNauOu54AnjJRJ4jPI5M4Pt3OTalVlPbufQ8hJbjyJqKepLjE2ftTN+H+be5mRwxbTslHE1AeOaneMeooTNlxjbfDl3StRMXDzmvjB7Hny8f9zsuYw2EdGL294/V+0c95AlbJ742DDrcZuqGdnry2subKYAuLyDhH2VTicJakCMzQLxNi601nMRjgdNCX3UFO9jirdxoUWc/nM1yCanhLIscyJO+gg+ixoRyUpBupgVRR01N7GVucSYlYmspahjMbZ4G1O4d9fEaJKeUy/ja2afVbPPJs+uXY2FPotLG9m7IEvYXIuxvZAXosYu88yjpWi59DXRdc+lWimv/q1tmYqoEQkTNtdibPcaXDiDYzNlE7MSq+nwN2v3e3GNOjIlUSMSJmzSfWycLXPFdNuWcO9e0sOslMKYXY2mOCOrwzePWhtEZUUlzxz4i6SP2qs7HmcDpVpU+GYS72NKj0bm0qjdn/0UV/TputiAd8AQ+eVRa4OoGZvUGJvvqfFoF4kUNl4+MWql6LC6nH9vwgA9kZ5TWih/x+w9RAmb1Bib/uN4pYMG5sv5qDMds1Ls1/dXXn/M3Lua6ERcpWHJ+JStfxZRwiY1xhbsAgoIswPblGdkRNfqva7uuRwbL0oOWUCUsEmKscX7WGRPAtuk55S+vr96W4qalWLpmyrrj/XReGSKQNSuyBI2ITE2HiBmZVMfMWOHfQhLVebSbOA79S+fTaZm57iHKGGTEGOb0gD5/PNJRJdKrl3gSrHlKhjm50usFOsD5ob9gz54P2bbIkrYxo6xcYegKYga0fV8d5mVzmazm8/kcxftInS86hHpXc/GRJSwjR1jm5yFoOX5DrdhHiPTZ50vIdlXNnY3pSnierOVvpElbCPE2NhWMClB+0G9K4pemgWpykvGjNHnEiBJ0AZROw+GjrGF2zDfTTBF5ss5BZuA0mOazwCqCidGm6u7H1+kcYGotUPUjG3IGBsGyIWmKhhEyFxKAmO2PaKEbagYG2eRpjJA9FFf9oT+xMjmyzl9vH9cdlS8X5aWCD7LZkrZehvIEraBYmwf7x+FwoM+k56vG6EZtVKXYov7kLJdhjiZcCBqjyNK2PqOsYXb8GK6HXl/pG3MbkpcraM8Ey1/Kco2DSCTKZYcsoEoYesrxma2GPORhSq5+83MZcWeS+mlisCFqZYcsoEoYesjxuZDyaFyjEwfdUGsgk3w0NLa1o4D0A/cPYsIovY0Y3SQqcN2x5/klHjRjafcUUnYZZs0GLMy8drH9vnn05mZmukjm81mBT+ZWqpCpdgM8RYvYV+lK2NWMqKWorZjbK5s86nykpUd/j5XGQHIfNpG1IzNRoxtrdYiM37pOaV4G+czMtOCMV/Ob2ZkfQ1utn+Ync/BuOSipiFqthA1Y+vqYzPrqEnjpi6ZMSPrqx5aFfqo8we+ROODmVo/iBK2LjG2sQeIWSmWhcOMhbF/TorFYgrmZOnAo9YfooTt2RjbGHXU0nNa+Ftmip7o1iMGIQGM6atEkqAfvIixBZtgkL6SHCNbqzUt3haXyrE/qJWiRCfiq2BMtZKJFOJ9nIclpI4RHxA1Y3skxsazo75mQhxcZ7GM9/FNx3TeQG6+Tzr4Mo0HqnMMhyhhaxtjMweITWEzK8WW+zIGm6DQ9xKAR4CoDYsoYWsTY7M1QMozMiK6KbJYFjEfRK0cGwT9A1EbHmvCFu/jS4zsp1sRz3zKHb5Nbjb53omxxdu40wAxq2CwiJkZKd+zU9wh3Pd/pyTGztZPFhv7snh/Gz/USmXRLirscSzvfTNfKz9ni2gXFX6m0n7L5JRY+1suoFYK+0wt0zRm+XxPbZxJwEpWlJ3zRJfl2kEf8o5PWZZRtIlIH/VNwUN+P1MVY2PHflvifUzx9uLuL9fwzwxnfzZAFlUS3LQGDAOPdczUxsHaUpS/NJUG1Jfie0zM4H85xmb2TaxquFuZuTT2XEa7CP6xH/jc+xAnlAw8akKwNfWjhnI6PCU3l6NV748212l9XfmWaBdlwSao/ExQT3JKcK56wFyK8vjFeR4fqzG2qgtqxt/MWAMR3cTAWKyq4m/lz+L3IX5xn+SU5DFPYA++WZhjtknUcB2GY5Zl3VNknG0rZys5xqVWKt8rSXTJTi7UopCdqyrdw0SbqDbbip/v/2yeV7VSpJZK1PG5+jPvCWaCTVC51OdsfFWbQ+4WxqEWXspiGdsRG+poLgv5jsTP1f2J8kyLiPDAw+lH1UysXP04OSWFmR4/yt8D0A0rZ7DuYiQ6aX2hqgYA6E6VFQfYoSxOiU5qX68az+WbP39fcI2601nYzC9OFSxYbeIK8P30A+ro90Nd/DjLbkWrinJcjn/G+O9OZ7uHTRsB4gr9UNWCD3Sn7rzyDhmii4+tDvZtqqUq/AzfW3esCVtdAUWf+3kCUIVZBaZJpD7ePyg9p3ni4PXlVUwhUufpOuWjhuk2vGZgapix4mjzmK1DrRSWoZZ4esZW3qJT/plT4ahoMCzl61C186Jc6RdLH3sUzn3FbpkmTEsU6MiziljOCFU9DvpgU4RBC+5ll5El7RecVxk8vQn+oA83m8rLD8QLhqdsEi3HOM2CBZngEuau02bsowVif8jqeQCsUA4JlOnSDQzYwex9AOwDYfMMjrGZNoNyZeDXl1dU+eiJNueVt001WUFANyBsnsEztPlynicOyrO2cBsiTNATfF6bbE58/pEo6A8Im4fwl+vj/YOI6CZ7TQQTaF+YTbHXal2Io3HrRiKY0ftGVDMX0B191Llo8ZeMmzkHmwBVdAfgoA95r4PF2yIXOvQ+GA4rZYuADLjicFZTDirLMlqrtfW2haAejnli6TksmLF5xOefz5vnzFhauA1JH/Wlvh0YhPlyDkEbAcTYPKJqr6EZ8+Hs6HyFLxrwGwibR/CSpwxmDGBqIMbmCVXxtfJrDC458B3M2Dwg3l4TBGUzLlFxOQpjLpgCmLE5Tnk2RlTdpJezo7jcYApA2AAA3oGlKADAOyBsAADvgLABALwDwgYA8A4IGwDAOyBsAADvgLABALwDwgYA8A4IGwDAOyBsAADvgLABALzj/wFC6oonz0gKVwAAAABJRU5ErkJggg==)
Khoảng cách giữa hai đường thẳng MN và B’D’ bằng
A. \(\sqrt 5 a\)
B. \(\frac{{\sqrt 5 a}}{5}\)
C. \(3a\)
D. \(\frac{a}{3}\)
Câu hỏi trên thuộc đề trắc nghiệm
Đề thi Thử THPT QG năm 2018 môn Toán Chuyên Đại Học Vinh