問題詳情:如圖,P為平行四邊形ABCD所在平面外的一點,過BC的平面與平面PAD交於EF,則四邊形EFBC是()A.空間四邊形 B.平行四邊形C.梯形 ...
2021-06-10 7078
1、Hewrotedownatelephonenumberonamemopad.2、Inthedream,hereachedfortheblueballpointpeninhisbreastpockettojotsomethingdownonhismemopad.3、Thephonehasanintegratedquicknotefunction,whichletsyoupullupasticky-sizememopadfromanypageonthedevice.4、Forexampl...
2023-12-28 12314
問題詳情:在四稜錐△PAD為正三角形,且平面PAD⊥平面ABCD.(1)求二面角P-EC-D的餘弦值;(2)線段PC上是否存在一點M,使得異面直線DM和PE所成的角的餘弦值為若存在,指出點M的位置;若不存在,請說明理由.【回答】知識點:點直線平面之間的位置題型:解答題...
2020-08-11 6460
Hoptothatlilypadinthesky,oldfriend.AgreenfrogsitsatopalargelilypadinthewatersofAtchafalayaDelta.WhenCharleysawWandahejumpedontoalilypad."Hi,"hecried.Hewasahandsomeprincebutawetone.Thelilypadhadcollapsedunderhisweightanddumpedhimintothewater.Oilspil...
2018-07-28 24943
Inthisarticle,bondingpaddesign,stencildesignandassemblyprocessofQFNdevicewillbeintroducedindetail.Thebondingpadofthecircuitboardisprovidedwiththegap,thegapandthepositioningholearespacedbycertainintervaltoavoidtinleaking....
2017-08-24 30135
Fixedthattheplayercharacterwouldmoveincorrectlyonthelandingpadifthepadwasflooded.TheritziesthotelinMuscatoffersahelicopterlandingpadoutback.Ifthethoughtofpublictoiletwatersplashingyourbacksidekeepsyouupatnights,fearnot-thesimplesolutionistocreateamin...
2017-07-17 4795
Thereportersreportedthatthelaunchpadwasonfireafterthelaunch.Themilitaryhasnotbeenabletodeterminetheexactlocationofthelaunchpad.Therocketexplodedonthelaunchpad,burningaliveandasphyxiatingengineers,designersandofficials.Thatlaunchmarkedtheinaugurationo...
2016-10-17 10236
1、scratchpadmemory2、scratchpadregister3、DoyouhaveascratchpadIcanwriteon?4、Theinventionrelatestoamulticolorscratchpad,acollatingmethodthereofandamulticolorscratchpadcollatingmachine....
2024-02-23 5145
問題詳情:如圖,四稜錐P-ABCD中,側面PAD是邊長為2的等邊三角形且垂直於底,,,是的中點。(1)*:直線平面;(2)點在稜上,且直線與底面所成角為,求二面角的餘弦值。【回答】【解析】試題分析:(1)取的中點,連結,,由題意*得∥,利用線面平行的判斷定理即可*得結論;(2)建立空間直角座標系,求得半平面的法向量...
2020-03-16 5224
問題詳情:.如圖,四稜錐P-ABCD中,側面PAD為等邊三角形且垂直於底面ABCD,AB=BC=AD,∠BAD=∠ABC=90°,E是PD的中點.(1)*:直線CE∥平面PAB;(2)點M在稜PC上,且直線BM與底面ABCD所成角為45°,求二面角M-AB-D的餘弦值.【回答】.(1)*取PA的中點F,連線EF,BF.因為E是PD的中點,所以EF...
2019-09-21 9839
問題詳情:如圖,在四稜錐P﹣ABCD中,底面ABCD是邊長為2的正方形,側面PAD⊥底面ABCD,且PA=PD=AD,E、F分別為PC、BD的中點.(Ⅰ)求*:EF∥平面PAD;(Ⅱ)求*:面PAB⊥平面PDC;(Ⅲ)線上段AB上是否存在點G,使得二面角C﹣PD﹣G的餘弦值為?說明理由.【回答】【考點】平面與平面垂直的判定;直線與平面平行的判定;二...
2022-04-18 19929
問題詳情:如圖,在四稜錐中,O為AC與BD的交點,平面PAD,是正三角形,,. (1)若點E為稜PA上靠A近的三等分點,*:直線平面PBC; (2)求*:平面平面PDC. 【回答】*: (1)因為,,所以.……………2分點E為稜PA上靠A近的三等分點,即,所以,.………………4分又因為平面PBC,平面PBC,所以...
2021-08-28 5579
問題詳情:小明喜歡利用pad聽歌,根據聲音的(選填“音調”、“響度”或“音*”)就判斷出是哪位歌手;音量太大會使耳膜受損,說明聲能傳遞 (“資訊”或“能量”),為此需要減小聲音的 (“音調”、“響度”或“音*”).【回答】【分析】聲音不但能傳遞資訊,還能夠傳遞能量;聲音的三個特徵分...
2020-10-19 26896
問題詳情:如圖,在四稜錐P-ABCD中,側面PAD為正三角形,底面ABCD為正方形,側面PAD⊥底面ABCD,M為底面ABCD內的一個動點,且滿足MP=MC,則點M在正方形ABCD內的軌跡為( ) A. B. C. ...
2019-10-25 21303
Whentypingonakeyboard,shouldbethewristpad,avoidwiththeforearmraised.Ensurethattheactivityisageappropriateandprovideprotectiveequipmentsuchashelmets,wristpads,andkneepads....
2018-07-26 27022
問題詳情:如圖,在四稜錐P-ABCD中,側面PAD為正三角形,底面ABCD為正方形,側面PAD⊥底面ABCD,M為底面ABCD內的一個動點,且滿足MP=MC,則點M在正方形ABCD內的軌跡為下圖中的【回答】A知識點:空間幾何體題型:選擇題...
2019-07-29 32973
問題詳情:如圖,平面PAD⊥平面ABCD,四邊形ABCD為正方形,∠PAD=90°,且PA=AD=2,E,F分別是線段PA,CD的中點,則異面直線EF與BD所成角的餘弦值為.【回答】 知識點:三角函式題型:填空題...
2019-12-10 11626
1、Theminutestickedby.Bobscribbledawayonthepad.2、Willbeflatonthecorrugatedboardflatonthepad.3、Giventhefactthatthetargetsiteis580kilometersfromShuangchengzi,itispossiblethataDF-15CtestseriesresultedintheHEimpactsonthepad....
2024-01-09 20425
Avoidingputtingyourelbowonhardsurfacesmayhelp,orwearinganelbowpadovertheulnarnerveand"funnybone"mayhelp.MayIborrowyourkneepadsandelbowpads?Ofcourse,besuretheyhaveonprotectivegear,includingahelmet,kneepadsandelbowpads....
2018-08-17 7358
問題詳情: 如圖,在四稜錐P-ABCD中,側面PAD為正三角形,底面ABCD為正方形,側面PAD⊥底面ABCD,M為底面ABCD內的一個動點,且滿足MP=MC,則點M在正方形ABCD內的軌跡為( )A. B. C. D.【回答】A【解析】試題分析:根據題意可知PD=DC,則點D符合“M為底面ABCD內的一...
2019-09-04 29070
問題詳情:如圖,四稜錐P-ABCD中,側面PAD是邊長為2的等邊三角形且垂直於底,是的中點.(1)*:直線平面;(2)點在稜上,且直線與底面所成角為,求二面角的餘弦值.【回答】(1)見解析;(2)【詳解】試題分析:(1)取的中點,連結,,由題意*得∥,利用線面平行的判斷定理即可*得結論;(2)建立空間直角座標系,求得半平面的法...
2020-09-14 23082
問題詳情: 如圖,在四稜錐P-ABCD中,底面ABCD為平行四邊形,己知AP=AC=AB=2,∠PAD=∠DAC=60°.(1)求*:AD丄PC;(2)若平面PAD丄平面ABCD,求二面角C-PD-A的餘弦值.【回答】知識點:點直線平面之間的位置題型:解答題...
2020-04-30 26988
Startbynotbuyingyourselfasketchpad.Comparedtothephonologicalloopandthevisuospatialsketchpad,thecentralexecutivemayhaveakeyroleinchildren'sarithmeticcognition.Comparedtothephonologicalloopandthevisuospatialsketchpad,thecentralexecutivemayhaveakeyrole...
2018-03-26 32956
問題詳情:如圖,在四稜錐P-ABCD中,底面ABCD為正方形,平面PAD⊥平面ABCD,點M線上段PB上,PD//平面MAC,PA=PD=,AB=4.(I)求*:M為PB的中點;(II)求二面角B-PD-A的大小;(III)求直線MC與平面BDP所成角的正弦值.【回答】(Ⅰ)詳見解析:(Ⅱ);(Ⅲ)【解析】試題解析:解:(I)設交點為,連線.因為平面,平面平面,所以.因為是正...
2021-10-03 17185
Shesmasheditusingthephone'sspecial'SWYPE'keypad,whichenablesuserstoinputtextwithouttheirfingertipleavingthescreen.Inwordprocessing,aseparatesetofkeysnumbered0through9onawordprocessor'skeyboardthatallowseasyentryofnumbers,aligningthemautomatically...
2018-08-15 25036