问题详情:如图,四棱锥P-ABCD中,侧面PAD是边长为2的等边三角形且垂直于底,,,是的中点。(1)*:直线平面;(2)点在棱上,且直线与底面所成角为,求二面角的余弦值。【回答】【解析】试题分析:(1)取的中点,连结,,由题意*得∥,利用线面平行的判断定理即可*得结论;(2)建立空间直角坐标系,求得半平面的法向量...
2020-03-16 5224
Thespaceshipwillliftofffromthelaunchingpadat7a.m.Thecenterpiecewasanornatemodelrocketonagreenfaunalaunchingpad.Usingthegrantfundingasalaunchingpad,projectsoftengoontoscaleuporreplicateelsewhere,winningprestigiousawardswithinthesphereofsocialentrepren...
2018-05-17 18086
telephonenumBerswrittenonapadShewroteonapadofpaper.NexttoPaulsen,NimGoldmandoodledthoughtfullyonapad.Heputonapadofgauzeandastripofadhesivetapeoverthewound.Mobilehomeortrailersmaybeonapadwhichyourentinamobilehomepark.Thechipsstorepersonaldatathatcanbe...
2022-03-24 8994
1、Hewrotedownatelephonenumberonamemopad.2、Inthedream,hereachedfortheblueballpointpeninhisbreastpockettojotsomethingdownonhismemopad.3、Thephonehasanintegratedquicknotefunction,whichletsyoupullupasticky-sizememopadfromanypageonthedevice.4、Forexampl...
2023-12-28 12314
问题详情: 如图,在四棱锥P-ABCD中,侧面PAD为正三角形,底面ABCD为正方形,侧面PAD⊥底面ABCD,M为底面ABCD内的一个动点,且满足MP=MC,则点M在正方形ABCD内的轨迹为( )A. B. C. D.【回答】A【解析】试题分析:根据题意可知PD=DC,则点D符合“M为底面ABCD内的一...
2019-09-04 29070
问题详情:小明喜欢利用pad听歌,根据声音的(选填“音调”、“响度”或“音*”)就判断出是哪位歌手;音量太大会使耳膜受损,说明声能传递 (“信息”或“能量”),为此需要减小声音的 (“音调”、“响度”或“音*”).【回答】【分析】声音不但能传递信息,还能够传递能量;声音的三个特征分...
2020-10-19 26896
问题详情:如图,在四棱锥PABCD中,平面PAD⊥平面ABCD,AB=AD,∠BAD=60°,E,F分别是AP,AD的中点.求*:(1)直线EF∥平面PCD;(2)平面BEF⊥平面PAD.【回答】*略知识点:点直线平面之间的位置题型:解答题...
2022-09-18 6826
问题详情:如图,在四棱锥P-ABCD中,侧面PAD为正三角形,底面ABCD为正方形,侧面PAD⊥底面ABCD,M为底面ABCD内的一个动点,且满足MP=MC,则点M在正方形ABCD内的轨迹为( ) A. B. C. ...
2019-10-25 21303
Thereportersreportedthatthelaunchpadwasonfireafterthelaunch.Themilitaryhasnotbeenabletodeterminetheexactlocationofthelaunchpad.Therocketexplodedonthelaunchpad,burningaliveandasphyxiatingengineers,designersandofficials.Thatlaunchmarkedtheinaugurationo...
2016-10-17 10236
Fixedthattheplayercharacterwouldmoveincorrectlyonthelandingpadifthepadwasflooded.TheritziesthotelinMuscatoffersahelicopterlandingpadoutback.Ifthethoughtofpublictoiletwatersplashingyourbacksidekeepsyouupatnights,fearnot-thesimplesolutionistocreateamin...
2017-07-17 4795
问题详情:如图,在四棱锥P-ABCD中,侧面PAD为正三角形,底面ABCD为正方形,侧面PAD⊥底面ABCD,M为底面ABCD内的一个动点,且满足MP=MC,则点M在正方形ABCD内的轨迹为下图中的【回答】A知识点:空间几何体题型:选择题...
2019-07-29 32973
问题详情:如图,四棱锥中,侧面PAD为等边三角形且垂直于底面ABCD,E是PD的中点.(1)*:直线平面PAB(2)点M在棱PC上,且直线BM与底面ABCD所成锐角为,求二面角的余弦值 【回答】知识点:点直线平面之间的位置题型:解答题...
2020-10-22 21489
Avoidingputtingyourelbowonhardsurfacesmayhelp,orwearinganelbowpadovertheulnarnerveand"funnybone"mayhelp.MayIborrowyourkneepadsandelbowpads?Ofcourse,besuretheyhaveonprotectivegear,includingahelmet,kneepadsandelbowpads....
2018-08-17 7358
Iusegroundedmousepad,IuseuniversalMATS,Iwalkbarefoot.AdvertisingGifts:advertisingmousepad,personalizedclothslippers,coasters,barMATS,wallpicture,flags,advertisingcapandsoon.Ifyou'realwaysjottingthingsdown,afreshnotepadanduncappedpenshouldbenexttoyou...
2017-12-25 18682
问题详情:在四棱锥P-ABCD中,AD∥BC,,G是PB的中点,△PAD是等边三角形,平面PAD⊥平面ABCD.(Ⅰ)求*:CD⊥平面GAC;(Ⅱ)求二面角P-AG-C的正弦值.【回答】知识点:点直线平面之间的位置题型:解答题...
2020-05-16 9872
Whentypingonakeyboard,shouldbethewristpad,avoidwiththeforearmraised.Ensurethattheactivityisageappropriateandprovideprotectiveequipmentsuchashelmets,wristpads,andkneepads....
2018-07-26 27022
1、Modernbrakesystemscanincorporatepressuresensorswhichdeterminebrakecylinderpressureorevenbrakepadpressure.2、Temperature-risinglawsofdrumbrakepadfortruckonlongdowngrades3、Imaginetheresultsifabrakepadmadeofsawdustwasinstalledinyourcar.4、Weareusedi...
2024-02-10 21240
Helostallhismoneyandhadtopadithome.Ididn'tbuysilkthread.Letherpaditfirst.Embroideryisthesameasyours.Howmuchisthemanualcostofembroidery?...
2018-11-18 17421
问题详情:如图,在四棱锥P﹣ABCD中,侧面PAD是正三角形,且与底面ABCD垂直,底面ABCD是边长为2的菱形,∠BAD=60°,N是PB的中点,过A、D、N三点的平面交PC于M,E为AD的中点,求*:(1)EN∥平面PDC;(2)BC⊥平面PEB;(3)平面PBC⊥平面ADMN.【回答】解:(1)∵AD∥BC,AD⊂平面ADMN,BC⊄平面ADMN, ∴BC∥平...
2019-11-26 31265
问题详情:如图,四棱锥P-ABCD中,侧面PAD是边长为2的等边三角形且垂直于底,是的中点.(1)*:直线平面;(2)点在棱上,且直线与底面所成角为,求二面角的余弦值.【回答】(1)见解析;(2)【详解】试题分析:(1)取的中点,连结,,由题意*得∥,利用线面平行的判断定理即可*得结论;(2)建立空间直角坐标系,求得半平面的法...
2020-09-14 23082
Startbynotbuyingyourselfasketchpad.Comparedtothephonologicalloopandthevisuospatialsketchpad,thecentralexecutivemayhaveakeyroleinchildren'sarithmeticcognition.Comparedtothephonologicalloopandthevisuospatialsketchpad,thecentralexecutivemayhaveakeyrole...
2018-03-26 32956
Scrubeachopticalsurfacewithagauzepadsoakedinacetone.Ihadtopayrushshippingformybirthkit—allthesterilizedgauzepads,alcoholswabs,glovesandgoopthemidwifeneedsatthebirth.Firstaidkit.Itshouldhavelatexgloves,gauzepads,thermometer,sterilebandages,band-aids,...
2018-09-30 5982
问题详情:如图,在四棱锥P﹣ABCD中,底面ABCD是边长为2的正方形,侧面PAD⊥底面ABCD,且PA=PD=AD,E、F分别为PC、BD的中点.(Ⅰ)求*:EF∥平面PAD;(Ⅱ)求*:面PAB⊥平面PDC;(Ⅲ)在线段AB上是否存在点G,使得二面角C﹣PD﹣G的余弦值为?说明理由.【回答】【考点】平面与平面垂直的判定;直线与平面平行的判定;二...
2022-04-18 19929
Asanitarybreastpadrelatestothetechnicalfieldofwomanhealth-carearticles,inparticulartoasanitarypadusedforkeepingthecircumferenceandclothesdryforwomeninlactationperiod.Forexample,mostgirlsinKatinecannotaffordsanitarypadsorachangeofclothes.Advertisingsa...
2018-05-13 7270
问题详情:已知四棱锥P-ABCD的顶点都在球O上,底面ABCD是矩形,平面PAD⊥平面ABCD,△PAD为正三角形,AB=2AD=4,则球O的表面积为()A. B. C.24π D.【回答】B令△PAD所在圆的圆心为O1,则易得圆O1的半...
2021-06-03 31138