填空题设

填空题若二次型f(x 1 ，x 2 ，x 3 )一2x 1 2 +x 2 2 +x 2 3 +2x 1 x 2 +tx 2 x 3 是正定的，则t的取值范围是________。

填空题Allmodernhumanoriginatedinsub-SaharanAfrica,accordingtoanewstudyboastedbyitsfoundersasthe"finalblow"againstanopposingviewpoint.Notsofast,saysoneanthropologistwhofindsflawsintheevidence.Thenewstudy,publishedintheJuly19issueofthejournalNature,deliverswhattheresearcherssaycouldbethefinalverdictinsupportofthesinglepoint"OutofAfrica"theory.Manicaandcolleaguestookmultiplemeasurementsofmorethan4,500malefossilskullsfrom105populationsaroundtheglobe.Theycombinedtheresultswithdatafromstudiesofglobalgeneticvariationsinhumans,findingthatbothgeneticandskullvariabilitydecreasedwithdistancefromAfrica.SopopulationsinsoutheasternAfricaheldthehighestvariabilitycomparedwithpopulationsinothercountries.Theresultsheldevenwhenthescientistsaccountedforclimate,sinceclimateconditionscanleadtochangesinskullfeatures."Inverycoldclimatesyoutendtogenerateaslightlythickerbrowridge.Whetherornotthat'stokeephorribleblizzardsoutofyoureyes,Idon'tknow,"Amossaid.Paststudiesbasedonskullmorphologyhavebeenweakandhavesupportedbothofthehumanoriginviews.Inhisownresearch,Hawksisfundingthatnaturalselectionhasledtochangesinthousandsofgenesduringonlythepastfewthousandyears."I'mreallythinkingjusttheoppositeofthispaper,"Hawkssaid."Therearedifferencesintheskullbetweenpopulations,includingtheirvariability,butitismostlyduetoveryrecenteffectsandnottheoriginofmodernhumans.""ThemuhiregionalideaisidenticaltotherecentAfricanoriginidea,exceptforitspredictionthatEuropeansandAsianswerepartofthesinglepopulationoforiginanddidn'tbecomeextinct."[A]"HumansseemtohavepouredoutofAfrica,spreadoutacrosstheworld,butatareallyquiteuniformratesuchthatyougetthislovelygraduallossofdiversity,"saidstudyteammemberWilliamAmosoftheUniversityofCambridge.[B]Allmodernhumansoriginatedfromthesameancestorsandtheykeptevolvingasthesocietyadvances.Somespeciesdiedoutbutothersremainedtoliveontheearth,whichisstillimpossibletosolve.[C]Attheendoftheday,aresolutiontothe"OutofAfrica"debatemaybeimpossible,hesaid.Mostoftheevidencecanbeinterpretedassupportingbothhuman-originstheories."It'sreallyhardtofindthetwo,"Hawkssaid.[D]Thisstudy"addsastronglineofevidencetotheOutofAfrica(hypothesis)usingsuchmorphology,"saidpaleontologistWillHarcourt-SmithoftheAmericanMuseumofNaturalHistoryinNewYork.Harcourt-Smithwasnotinvolvedinthecurrentresearch.[E]Debateovertheoriginsofmodernhumanshassimmeredamonganthropologistsforyears,withonetheoryassertingthatHomosapiensmigratedacrosstheworldfromasinglepointinAfrica.TheothertheorystatesthatmultiplepopulationsofHomosapiensindependentlyevolvedfromHomoerectusinregionsbeyondAfrica.[F]TherecentstudywasfundedbytheBiotechnologyandBiologicalSciencesResearchCouncil.Ithasprovidedconclusiveevidenceconcerningtheactualprocessofhumanevolution.[G]"Wehavecombinedourgeneticdatawithnewmeasurementsofalargesampleofskullstoshowdefinitelythatmodernhumansoriginatedfromasingleareainsub-SaharanAfrica,"saidleadresearcherAndreaManicaoftheUniversityofCambridge.41.______42.______43.______44.______45.______

填空题设f(x)在点x=0处可导，且，则f'(0)=______。

填空题sin2xcos4xdx=______．

填空题圆周x2+y2=16与直线L：+y=4围成的小的那块弓形状的图形绕该直线L旋转一周生成的旋转体(形如橄榄状)的体积V=________．

填空题设f（x）=，则f"（x）=________。

填空题设函数f（u）可微，且f"（2）=2，则z=f（x 2 +y 2 ）在点（1，1）处的全微分dz=________。

填空题设y=y(x)是由方程x 2 +y=tan(x-y)所确定且满足y(0)=0，则y"(0)=______．

填空题=________．

填空题某企业生产某产品，在单位时间上分摊到该产品的固定成本为c 0 元．又设在单位时间内生产x件产品的边际成本为ax+b(元/件)，a＞0，b＞0，均为常数，则成本函数c(x)=______．

填空题设f(x)在(-∞，+∞)上可导，，又，则a=________．

填空题已知反常积分=________．