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Module1BritishandAmericanEnglish（ReadingandSpeaking）

Module1BritishandAmericanEnglish（ReadingandSpeaking）

Step1Lead-in.
theteacherssays:
Asyouknow,Chinaisbiginsizeandfullofmanydialects.HongKongispartofChina.DoyouthinkwewillhavedifficultyinunderstandingpeoplefromHongKong?WhatdifficultiesinunderstandingdoyouthinkpeoplefromHongKongwillhavewhentheyareinBeijing?DopeoplefromShanghaisoundthesameasthosefromXi’an?WhataboutChinesecharacters?DoyouthinkpeoplefromdifferentregionsofChinahavedifficultyinunderstandingChinesecharacters?WhataboutBritainEnglishandAmericanEnglish?Doyouthinktheyarequitedifferent?Canpeoplefromthetwocountriesunderstandeachother?
Step2Finishactivity2.
ReadthepassageandfindwaysinwhichBritishandAmericanEnglisharedifferent.Theansweris:vocabularyspellinggrammarandpronunciation.
Step3Readthefirstpartandfindoutthetopicsentence
Thefirstandmostobviouswayisinthevocabulary.
Whatistheexample?Americansdriveautomobilesdownfreewaysandfillupwithgas.TheBritishdrivecarsalongmotorwaysandfillupwithpetrol.Asatourist,youwillneedtousetheundergroundinLondonorthesubwayinNewYork,ormaybeyouwillprefertogetaroundthetownbytaxi(British)orcab(American).
Letthestudentscomparethedifferencesinvocabularyandfillintheblanks.
Step4Thesecondpartofthepassage.
Americansuseaflashlight,whilefortheBritish,it’satorch.TheBritishqueueup;Americanstandinline.Sometimesthesamewordhasaslightlydifferentmeaning,whichcanbeconfusing.Chips,forexample,arepiecesofhotfriespotatoinBritain;inthestateschipsaresoldinpackets.TheBritishcallthesecrisps.ThechipstheBritishknowandloveareFrenchfriesontheothersideoftheAtlantic.
Themainideaofthisparagraph:Sometimesthesamewordhasaslightlydifferentmeaning,whichcanbeconfusing.
Step5Thethirdpart
thetopicsentenceis:thereareafewdifferencesingrammar.Accordingtothetextsandtellussomeexample.
TheBritishsay:Haveyougot…?Myfriendhasjustarrived.intheteamattheweekendI’llseeyouonMonday.
Americanssay:Doyouhave…?Myfriendjustarrived.ontheteamontheweekend.I’llseeyouMonday
Step6Thefourthpart
Thedifferenceisspelling,suchascenter,color,andprogram(AmericanEnglish)centre,colour,andprogrammes(BritishEnglish)
Whatdoesthesentencemean?
TheBritishandtheAmericansaretwonationsdividedbyacommonlanguage.英国和美国是被同一种语言分开的两个民族。
Step7Thefifthpart
Whatisthemainideaofthefirstparagraphofthispart?
ItsaysthetwovarietiesofEnglisharemovingcloser.
Whatisthereason?
ThereasonisthatformorethanacenturycommunicationacrosstheAtlantichavedevelopedsteadily.
WilltherebemorethantwovarietiesofEnglish?Notjusttwomainvarieties.
Step8Listentothetape.
Step9completethesentenceswiththecorrectwordsorphrases.
1.Thereare______differencesbetweenAmericanandBritishvarietiesofEnglish.
A.noB.afewC.lotsof
2.Americans________understandwhattheBritisharesaying.
A.sometimesB.usuallyC.never
3.Thereare_________differencesbetweenBritishandAmericangrammar.
A.noB.manyC.notmany
4.Americanspellingis_____Britishspelling.
A.thesameasB.simplerthanC.harderthan
5.ForaLondoner,anAmericanaccentmaybeeasiertounderstandthan_______.
A.aChineseaccentB.someBritishaccentsC.aCNNnewsreader.
6.TelevisionandtheInternethavemadeit______fortheBritishandAmericanstounderstandeachother.
A.harderB.easierC.impossible
thekey:1.B2.B3.C4.B5.B6.B
Step10listentotherecordingofaprogramofBBCandVOA.LetstudentsjudgethespeakerisBritishorAmerican.
Step11MatchtheBritishandAmericanwordsinthebox.
apartmentautumnelevatorfallfirstfloorflashlightflatgarbagegasgroundfloorholidayliftstandinlinelorrypavementpetrolqueueuprubbishsidewalktorchtruckvacation
BritishEnglish:flatautumnliftgroundfloortorchrubbishpetrolholidayqueueuplorrypavement
AmericanEnglish:apartmentfallelevatorfirstfloorflashlightgarbagegasvacationstandinlinetrucksidewalk
RewritethesentencesusingBritishwords.
1.Wereallylikegoingonvacationinthefall.
2.Youdon’tneedtotaketheelevator.Ourapartmentinonthefirstfloor.
3.Didyouseethattruckcomeoutofthegasstation?
4.Passmeaflashlight,Eddie.I’velostmywallet.
Thekey:
1.Welikegoingonholidayintheautumnverymuch.
2.Youdon’tneedtousethelift.Ourflatisonthegroundfloor.
3.Didyouseethatlorrycomeoutofthepetrolstation?
4.Passmeatorch,Eddie.I’velostmywallet.
Step12Homework.Recitethemainimportantsentencesinthepassage.

BritishandAmericanEnglish教案

高二英语必修五Module1BritishandAmericanEnglish导学案
ModuleSummary—单元小结
学习目标Learingaims:①Understandsomesentencesorparagraphscontainswordsandstructureswehavelearnedinthismodule.
②Identifysometenses:ThePresentIndefinite,ThePresentContinuous,ThePresentPerfectandsoon.
学习重点LearningImportant：
①Expressthemeaningusingallkindsoftenses.Forexaplethe
PresentIndefinite.
②Analyse,intergradethelanguagematerialsbywaysofscaningtoacquiretheusefulinformation.
知识链接Knowledgelinks:OtherusagesofthePresentContinuous:
①一些非延续性动作，可用现在进行时表示很快将发生的事情。
Thebusisstopping.(表示渐渐停下来，很快将全部停止)
②现在进行时可以表示按计划、安排将要发生的动作。
We’regoingtoLondonthedayaftertomorrow.
学法指导Guidanceoflearning:Knowaboutthebasicusagesofverbinthetext.
探究过程Processesofexploring:
PARTⅠSimplesentencescorrection(单句改错)（知识应用B级）
1.Thanksforyourhelp,wegotoverthesedifficulties.
2.Allthestudentswereinfavorwiththereform.
3.QiBaishiisreferredasthePicassoofChina.
4.Thisdictionaryisbelongedtome.
5.Howdoyouliketheideapresentingbytheheadteacher.
6.Youmayfinditnecessarytofinishtheworkaheadoftime.
7.Doyouknowwhetherthisprogramisintheair?
8.Theoldmangotusedtolivealone.
9.Theyoungcouplemadeafusstotheirpetdog.
10.Howareyougettingonyourjobhere?
PARTⅡUseproperprepositionoradverbtocompletethesentences.（B级）
1.Thetwinshaveeverythingincommonwitheachother,_______character.
2.Thebasketisfilled_______flowers.
3.Itispolitetoqueue_________whileyouwaitatthestation.
4.Compared________lastyear,hemadegreaterprogressthisyear.
5.Hedidn’tgotoHuanggangMiddleSchool.________heleftforBeijingNo.4Middleschool.
6.Whathesaidled_________thisquarrel.
7.Thelightwillbeon________theflickofswitch.
8.Goodsleepinghasagoodeffect_________yourhealth.
9.Itishelpfulforchildrentpresenttheirthoughts__________theirparents.
10.NoahWebstergraduated__________YaleUniversity.
PARTⅢChoosethebestwaytofillintheblanks.(C级)
1.Doyouburncoal_________gasforcookinginwinter?
2.Don’tblamehimforbreakingthatvase,__________heisachild.
3.Thegarden__________apathisreallyabigone.
4.Heisthebestplayer_________withoutquestion.
5.Ipickedupawallet__________moneyandturneditin.
6.Thereisanewstore________ofthestreet.
7.Rememberwearefriends_________youare.
8.Thestudentsarenow_________togettheirnewbooks.
当堂检测Haveain-classtest
●MultipleChoice（C级）
1.Ourancestors(祖先)celebrated______birthof_____childbygivingredeggs.
A.the,aB.the,theC./,aD./,the
2.–-Ijusthearthattheticketsfortonight’sshowhavebeensoldout.
--Oh,no!_________.
A.Idon’tmindB.Iknewitalready
C.IwaslookingforwardtothatD.It’snotatallinteresting
3._________wasonceregardedasimpossibleisverycommontoday.
A.ThatB.WhichC.WhatD.Who
4.Wheretherearesmallchildrenaround,itisnecessarytoputbottlesof
pillsoutof___________.
A.handB.reachC.holdD.place
5.I__________himtotakethejob,butIdidn’tsucceed.
A.persuadedB.triedtoadvise
C.didmybesttomakeD.triedtopersuade
6.Chinaislargerthan___________countryinAfrica.
A.anyotherB.anyC.otherD.theother
7.Americanseat________astheyactuallyneedeveryday.
A.twiceproteinasmuchB.proteinasmuchtwice
C.proteinastwicemuchD.twiceasmuchprotein
8.__________atthedoorbeforeenteringplease.
A.KnockB.ToknockC.knockingD.Knocked
9.Annawasreadingapieceofsciencefiction,completely_________tothe
outsideworld.
A.havingbeenlostB.tobelostC.lostD.losing
10.Look!There_________ahillinfrontofthevillageinthepainting.
A.standsB.beC.livesD.lies
●ReadingField（能力提升D级）
IfAmericancustomsseemstrange,rememberthatAmericansfeelthesamewaywhentheyvisitanothercountry,peoplelivingindifferentculturesdomanydailythingsdifferentlyfromoneanother.Whatadull(notinterestingorboring)theworldwouldbeifthiswerenottrue!
Somedifferencesaresmall,andonesoonbecomesusedtothem.Forexample,manypeoplefinditstrangethatAmericansmovefromplacetoplacesooften.Borninonecity,theymayattendschoolinasecond,enterbusinessinathird,andperhapsmoveseveraltimesduringtheirlives.Today,mostAmericansfullyexpectandacceptthefactthattheywillmovefrequently.
However,housesareofgreatinteresttoAmericans.Theyspendalotoftimethinking,readingandtalkingabouttheirhomesandhowtoimprovethem.Theyalsoenjoylookingatotherpeople’shouses,sincetheywouldenjoyvisitingandexaminingahouseinanothercountry,theymaysupposethatyouwillprobablyhavethesamedesire(strongwish)whenyouvisittheUnitedStates.SodonotbesurprisedwhenyouvisitanAmericanfamilyandareshowneveryroominthehousebesidesthebathroomandkitchen.
1.Thefirstparagraphsuggeststhat___.
A.onlyAmericancustomsprovetobestrange
B.customsaredifferentindifferenttimes
C.customsaredifferentfromcountrytocountry
D.Americansfeeluneasywhentheyvisitanothercountry
『分析』

2.Accordingtothepassage,theworldwouldbeterriblydullif___.
A.peoplelivingindifferentcountriesdidalotofthingsinthesameway
B.peoplelininginvariousregionsintheworlddidafewdailythingsin
thesameway
C.thepeopleallovertheworldspokethesamelanguage
D.mostoftheworldpeoplediddailythingsdifferentlyfromoneanother
『分析』

3.MostAmericansthinkitnormalthat___.
A.theworldisnotdullB.theywillmovefrequently
C.theydomanydailythingsdifferentlyfromoneanother
D.customsaredifferentfromcountrytocountry
『分析』

4.WhichofthefollowingstatementisNOTtrue?
A.Americansperhapsmoveseveraltimesduringtheirlives
B.Americansenjoyvisitingothers’houses
C.IttakesAmericansmuchtimetothink,readandtalkabouttheirhousesandhowtoperfectthem
D.YouareshowingalltheroomsinthehousesexceptthebathroomwhenyouvisitanAmericanfamily
『分析』
总结Summary：
Introspection:________________________________________________________

BritishandAmericanEnglish教学案

BritishandAmericanEnglish教学案
Module1BritishandAmericanEnglish
PeriodOne
Step1.Lead-in
1.Doyouliketravelling?
Haveyoueverbeentotheothercountries?
WhatdoyouknowaboutBritainAmerican?
(Askstudentstospeakoutasmanyastheycan)
2.What’sthedifferencebetweentheUKandtheUSA?(TheteachercanshowtheSssomepicture.)
(AsktheSstowritedownthedifferencesandcheckwiththeirpartner)
Step2.Warming-up(Introduction)
1.ReadtwoEnglishlettersanddecidewhichiswrittenbyanAmerican.
2.Comprehendquotationsaboutthedifferences.
Step3.Fastreading
1.Helpstudentstograspthemainideaofthetextbydoingthetask.
2.ReadthetitlesandthefirstsentencesofeachparagraphandfindfourwaysinwhichBritishandAmericanEnglisharedifferent.
Step4.Readingfordetailedinformation
1.Readpara.1andfillintheform.(Theformisonthenextpage)
2.Dosometrueorfalsequestionsandchecksomedetailedinformation
(1)There’realotofdifferenceingrammarbetweenBritishandAmericanEnglish.
(2)Spellingisthefirstandmostobviousdifferencebetweenthetwo.
(3)Britishpeoplesay”writeme”and”ontheteam”.
(4There’snotmuchvariationinlanguagewithinthecountry.
(5)TelevisionandInternethavemadeiteasierfortheBritishandAmericanstounderstandeachother.
(6)Inthefuture,there’llbeonlyonekindofEnglish.
3.Beautifulsentences:tolearnsomeimportantstructures
Step5.Practise
1.fillintheblankswithsomekeywords
There’refourwaysinwhichBritishandAmericanEnglish________fromeachother.Thefirstandmost________wayisinthevocabulary.Ingrammarthere’reafew__________.TheBritishsayHaveyougot…?______AmericanspreferDoyouhave…?TheBritishuseprepositions______Americanssometimes______them.Theothertwoareasinwhichthetwo_________aredifferentarespellingandpronunciation.Butformorethanacenturycommunicationshavedeveloped_______.ThankstosatelliteTVandtheInternet,ithasbeenpossibletolistentomanyEnglishmenatthe______ofaswitch.Soexpertsbelievethatthetwoaremoving______.
3.Retellthetextaccordingtoit.
4.Discussion
Whichofthefollowingdoyouthinkisthebestlanguageinthefuture?Why?
BritishEnglish,AmericanEnglish,worldEnglish,Chinese
Step6.Vocabulary
Task:RewritethesentencesusingtheBritishwords.
1.MatchtheBritishandAmericanwordsandphasesinthebox..
2.Askthestudentstoreadtheiranswersoutandcomparewiththeirpartners.
3.RewritethesentencesusingBritishwords..
4.Summarize:andPractice:
Step7.Openwork
TrytofindinformationaboutChineseandprepareareporttointroducethefollowingthreeaspectsofChinese.
1.Thewritingsystem
2.VarietiesofChinese
3.Languagetoday

PeriodTwo

Step1.Grammar1
Task1:Findouttheusesoftheverbs.Rulesofthetenses.
Activity1.Matchthesentenceswiththecorrectmeanings.
Activity2.completethesentenceswiththecorrectformoftheverbs.
Activity3.Telltheusesoftheverbs.Rulesofthetenses
(1)Completethesentencesinyourownwords.
(2)Observe,compareandfindouttherules.
：I____ping-pangquitewell,butIhaven’thadtimetoplaysincethenewyear.
A.willplayB.haveplayedC.playedD.play
：—You’redrinkingtoomuch.
—Onlyathome.Noone________mebutyou.
A.isseeingB.hadseenC.seesD.saw
2.Canyouexplainthefollowinguseoftenses.
presentsimpletense
presentcontinuoustense
presentperfecttense
futuretense
Step2.Function
Task:Givingreasons
Directions:
1.Underlinethewordswhichintroducereasons.
2.Answerthequestions.
3.Completethesentenceswithbecausesinceasornowthat.
Step3.Test
Completethemessageswiththecorrectformoftheverbs.
HiMum,
Hopeyou__________(be)well.I________(have)alovelytimeinNewYork.Tomorrowwe___________(go)toseethefireworks.It’shardtounderstandtheaccenthere,butit________(get)easier,asI_________(be)herefor3weeks.Nextweekwe_________(fly)toMexicowherethey________(speak)noEnglishatall,justSpanish.I__________(Spend)nearlyallthemoneyyougaveme!
Love,XiaoPing
Practice:Makeyourownsentencescreatively,usingbecause,since,asornowthat.
Step4.EverydayEnglish
Task:Usethephrasesfreely.
1.Remindthestudentsoftheexpressionsthatwehavelearned.
2.Askthestudentstorememberthem.
3.Speakingpractice:
Haveaconversationusingsomeofthephrases.
Step5.Homework
Haveagoodrevisionoftoday’slessonandmakesentenceswiththetensesandvariouswordstoexpressreasons.It’sbettertodosomerelatedexercises.

PeriodThree

Step1.Warmingup:Talkabouttheproblemsexchangestudentshave.
understandingthelanguage
gettingonwithpeople
food
differentschoolsubjectsandtimetable
localcustoms
climate
Step2.Presentation
Listentothetargetlanguage:
VocabularyandListening–2.Listeningtothe1stpart(5m)Listenandcompletethepassage.
Hello,andwelcometotoday’seditionofIntheair.Asyouknow,everyweekonthisprogrammewediscussanaspectofthewaywe__1____now,andtoday’stopicisthelanguagewe____2____-English.Sothat’ssomethingwhichaffectsusall.Thequestionis,what’sgoingto__3___tothewaywespeakEnglishinthefuture?AreweallgoingtospeaklikeAmericans?OrwillBritishEnglishcontinueto_4___?Lateronwe’regoingto_5___youtophoneinand__6___yourviewsonthesubject,butfirstwe’regoingto__7___totwoyoungpeople,oneAmerican,andoneBritish,whohavespenttimeonaneducationalexchangeintheother’scountry.We__8___theywillhavesomeinterestingideasonthesubject.
Playagaintoanswerthequesrions.Makenotesifnecessary.(Activity4)
Havethestudentscomparetheanswerinpairs.
Playthetapeathirdtimeforafinalcheck.
Checknoteswiththeteacher.
Step3.SpeakingandWriting
1.Reviewthecontentofthetextbyaskingsomequestions.
InhowmanywaysareAmericanEnglishandBritishEnglishdifferent?
Whichisthefirstandmostobviousway?
......
2.Thegreatdebate
Workingroups.Readthenotesanddecidewhichisthebestvarietyoflanguageinthefuture.
Giveyourreasons.
BritishEnglish,AmericanEnglish,WorldEnglishChinese
3.Writing
WriteapassageaboutyourfavouritechoiceandthereasonsinthediscussionaboveorwritethreemoreparagraghsabouttheChineselanguage(activity4onP8).
Step4.Homework
GetmoreinformationaboutthelanguagethroughtheInternetorothermethodtosupportyourcomposition.

PeriodFour

Step1.Culturalcorner
1.Readthetextquicklyandmatcheachparagraghwiththecorrectmainidea.
2.Appreciateandanalyze2or3longsentences.
Step2.ModuleFile
1.Review:Gooverthevocabularyandgrammarfocusinthemodulefile.
2.Put“?”nexttothethingsyouarenotsureof.Thensolvetheproblemsingroupsorraiseyourquestions.
3.Dosomeexercisestoconsolidatewhatwelearnedinthismodule.
Step3.Homework
Recitethephrasesandsentencepatterns.

Period3:Grammar—Reviewofverbforms(1)
Goals
●ToreviewPresentsimple,presentcontinuous,presentperfectandfuturereference;forandsincewithpresentperfect
Procedures
▇ReviewingPresentsimple,presentcontinuous,presentperfect
ActiveTenses
SimplePresent
PresentActionorConditionGeneralTruthsNon-action;HabitualActionFutureTime
Ihearyou.
Herecomesthebus.TherearethirtydaysinSeptember.Ilikemusic.
IrunonTuesdaysandSundays.Thetrainleavesat4:00p.m.
PresentProgressive
ActivityinProgressVerbsofPerception
IamplayingsoccernowHeisfeelingsad
PresentPerfect
WithverbsofstatethatbegininthepastandleaduptoandincludethepresentToexpresshabitualorcontinuedactionWitheventsoccurringatanindefinitedorunspecifiedtimeinthepast--withever,never,before
THEPASSIVETENSES
Simplepresent
active:passive:
Thecompanyshipsthecomputerstomanyforeigncountries.Computersareshippedtomanyforeigncountries.
PresentProgressive
active:passive:
Thechefispreparingthefood.Thefoodisbeingprepared.
PresentPerfect
active:passive:
Someonehasmadethearrangementsforus.Thearrangementshavebeenmadeforus.
■UsingthePresentPerfectTense:FORorSINCE?
WeusePresentPerfecttensetotalkaboutactionwhichstartedinthepastandcontinuesuptothepresent.
Examples
Ihavehadthiscomputerforaboutayear.
Howlonghaveyoubeenatthisschool?
IhaventseenJuliasinceSeptember.
Tip!ForotherusesofthePresentPerfecttense,seethePresentPerfectTense-WhenToUse.
Weuseforwithaperiodoftime,forexample:afewdays,halfanhour,twoyears.Weusesincewiththetimewhentheactionstarted,forexample:lastyear,June8,Imetyou.
Eachofthesepresentperfectsentencescontainsatimeexpression.Eachtimeexpressionisalengthoftime(whichrequiresFOR)orastartingtime(whichrequiresSINCE).
1Mayahasbeenaprofessional________1989.
2Sofar,ithasrained________fivehours.
3Ihaventbeensnowboarding________lastwinter.
4Johasbeenastudenthere________March.
5ThebeaverhasbeenanemblemofCanada________manyyears.
6CougarshavealmostdisappearedfromtheVictoriaarea________humanssettledhere.
7Maryhaskeptadiary________shewastenyearsold.
8FirstNationspeopleinBritishColumbiahavetoldstoriesabouttheeagle________hundredsofyears.
9TheCanadiantwo-dollarcoin(ortoonie)hasbeenincirculation________1996.
10Theyvebeenmarried________twenty-fiveyears.
11Ihaventphonedhome______Christmas.
12Wevebeenhere__________nineoclock.
13IhaveworkedforInternationalHouse__________morethaneightyears.
14Ihaventvisitedmyhometown_________Ileftschool.
15Ihaventbeentothecinema__________ages.
16Ihavestudiednon-stop_________9.15.
17Ihavehadadrivinglicence_________Iwaseighteen.
18Shehasnthadadayoff_________1999.
19JohanhasbeeninEngland__________morethantwoweeksnow.
20Peterhasbeenmybestfriend_________wewerenine.
■Closingdownbydecidingifyouneedfororsincewiththesetimeexpressions.
---for/sincelastweekend
---for/sincetenseconds
---for/sinceChristmasEve
---for/sinceadecade
---for/sinceIfinishedschool
---for/sinceacoupleofdays
---for/sincemybirthday
---for/sincealongtime
---for/sincetencenturies
---for/sincethe70s
---for/sinceIwasaboy
---for/sinceAugust
---for/sincethelastmonth
---for/sincefifteenyears
---for/sincetenseconds
---for/sinceChristmasEve
---for/sinceadecade
---for/sinceIfinishedschool
---for/sinceacoupleofdays
---for/sincemybirthday
---for/sincealongtime
---for/sincetencenturies
---for/sincethe70s
---for/sinceIwasaboy
---for/sinceAugust
---for/sincethelastmonth
---for/sincefifteenyears
---for/sincetheaccident
---for/sincethen
---for/sinceweboughtthishouse
---for/sincelastmonth
---for/sinceamillennium
---for/sinceImetyou

对数（1）教案苏教版必修1

一名优秀的教师在教学方面无论做什么事都有计划和准备，作为教师就要在上课前做好适合自己的教案。教案可以让学生们能够在上课时充分理解所教内容，让教师能够快速的解决各种教学问题。那么如何写好我们的教案呢？以下是小编为大家收集的“对数（1）教案苏教版必修1”欢迎大家阅读，希望对大家有所帮助。

3.2.1对数（1）
教学目标：
1．理解对数的概念；
2．能够进行对数式与指数式的互化；
3．会根据对数的概念求一些特殊的对数式的值．

教学重点：
对数的概念，对数式与指数式的相互转化，并求一些特殊的对数式的值；
教学难点：
对数概念的引入与理解．

教学过程：
一、情境创设
假设2005年我国的国民生产总值为a亿元，如每年平均增长8%，那么经过多少年，国民生产总值是2005年的2倍？
根据题目列出方程：______________________．
提问：此方程的特征是什么？已知底数和幂，求指数！
情境问题：已知底数和指数求幂，通常用乘方运算；而已知指数和幂，则通常用开方运算或分数指数幂运算，已知底数和幂，如何求指数呢？
二、数学建构
1．对数的定义．
一般地，如果a(a＞0，a≠1)的b次幂等于N，即ab＝N，那么就称b是以a为底N的对数，记作logaN，即b＝logaN．
其中，a叫作对数的底数，N叫做对数的真数．
2．对数的性质：
（1）真数N＞0，零和负数没有对数；
（2）loga1＝0(a＞0，a≠1)；
（3）logaa＝1(a＞0，a≠1)；
（4）a＝N(a＞0，a≠1)．
3．两个重要对数：
（1）常用对数(commonlogarithm)：以10为底的对数lgN．
（2）自然对数(naturallogarithm)：以无理数为底的对数lnN．
三、数学应用
例1将下列指数式改写成对数式．
（1）24＝16；（2）；（3）；（4）．
例2求下列各式的值．
（1）log264；（2）log832．
基础练习：
log10100＝；log255＝；
log2＝；log4＝；
log33＝；logaa＝；
log31＝；loga1＝．
例3将下列对数式改写成指数式
（1）log5125＝3；（2）log3＝－2；（3）lga＝－1．699．
例4已知loga2＝m，loga3＝n，求a2mn的值．
练习：
1．（1）lg(lg10)＝；（2）lg(lne)＝；
（3）log6[log4(log381)]＝；（4）log3＝1，则x＝________．
2．把logx＝z改写成指数式是．
3．求2的值．
4．设，则满足的x值为_______．
5．设x＝log23，求．
四、小结
1．对数的定义：b＝logaNab＝N．
2．对数的运算：用指数运算进行对数运算．
3．对数恒等式．
4．对数的意义：对数表示一种运算，也表示一种结果．
五、作业
课本P79习题3.2(1)1，2，3(1)～(4)．