Mathcad PrimerMathcad手册Word文件下载.docx

Mathcad PrimerMathcad手册Word文件下载.docx

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ImportantWarningaboutTypicalScientificSymbols6

SelectingandEditing7

VariableNames7

Units8

DefiningYourOwnUnits9

EasyGraphs10

RangeVariablesandGraphs12

ZoomandTraceFunctionsinaGraph14

DataandDataFiles:

ExcelData15

EnteringDataintoMathcad16

CopyingDatafromEXCEL17

NumericalCalculations17

NumericalRootsofEquations18

SymbolicCalculation19

SymbolicIntegration20

TheAssumeKeyword21

PartialDerivatives22

SolvingEquations22

TheMathcadWindow

WhenyoustartMathcad,thescreenshouldappearasshownbelow.Aseriesofmenuitemsarelisted,andunderneaththemenuaretoolbars.AnancillarytoolbarcalledMathappearstotheright.Inthisdocument,menucommandswillbenotedasItem1,item2,andsoforth.Asanexample,theprintpreviewcommandwouldbetypedas:

File,PrintPreview.ToexecutethecommandyouwouldpointtoFile,thenselectPrintPreviewfromthedrop-downlist.

Ifyoudonotseealltheitemsinthegraphic,gotoView,Toolbars,andselectthetoolbarsthatyouwishtosee.Yourfirstassignmentistocheckthevariousmenuitemstoseewhattheycontain.

Thepageboundaryshowsyouwhatwillfitonanormalpagewhenthedocumentisprinted.Materialtotherightoftheboundarywillprintonthenextpage.

ThetoolbarunderthemenuistheStandardtoolbarandcontainsiconsfor:

Newdocument,Opendocument,Save,Print,PrintPreview,andsoon.Theseiconshavetooltips（littletagsthatinformyouoftheirfunctions）.Ifyouforgetwhatanicondoes,holdthemousepointeroveritforasecondandthetooltipwillappear.

Notetheredcrosshairinthedocumentwindow.ThisistheinsertionpointinMathcadandanytypedinformationwillappearatthispoint.Clickingthemouseinanewlocationmovestheinsertionpoint（tryit!

）.

EnteringText

InMathcad,textisdifferentfrommathematics.Textinformationandmathinformationhavetheirseparatefonts,colors,andstyles.Theformattingtoolbar（theonerightabovetheactualdocument）hasastyleboxthatinformsyouofthetypeofinformationthatisbeingtypedorselectedinthedocument.Thedefaultstyleisvariablessowhenyoutype,Mathcadassumesyouaretypingmathematics.

Ifyouwishtotypetext,firsttypeaquotationmark,“.ThequoteopensatextregioninMathcadandyoucantypeanytextthatyouwish.Clickanywhereoutsidethetextregiontostop.

AnygoodMathcaddocumentshouldcontaintexttoannotateandexplainthecalculations.Youcan,andshould,changetheappearanceoftexttodistinguishitfrommath.YoucandothisbytypingFormat,Style.Thisbringsuptheformatdialogbox.Tochangethetextfont,chooseNormalandclickmodify.Clickthefontboxandyoumaychangethefontstyle,size,andcolor.Agoodchoiceistomaketextfontadifferentcolorthantheblackfontusedforvariables.

EquationsandVariables

Mathematicalexpressionsaretypedintheusualway,usingthe+,–,/,and*keysforaddition,subtraction,division,andmultiplication.Exponentsareenteredwiththe^key.Youmustremembertoincludethemultiplicationsymbolinallexpressions.Mathcadwillinterpretxyasanewvariable,andnotastheproductofxandy.Herewetype5*12=andyoucanseetheresultis60.Ifwetype512=Mathcadinterpretsthesecondstatementasthenumber512asyoucanseefromtheresult.

Forgettingthemultiplicationsymbol（*）isthemostcommonsourceofheadachesforMathcadbeginners.

AconvenientwaytoseemultiplicationistogotoTools,Worksheetoptions,Display.Ifyoumakethemultiplicationsymboladot,largedot,or,itwillbehardtomiss.

Youmustfirstdefineavariablebeforeyouuseitinacalculation.Intheexamplebelow,xisnotdefinedatthebeginningandishighlightedbyMathcadinred（anerror）:

Todefineavariable,usethe:

=operator.Youenterthisbytypingacolon.The:

=isanassignmentoperatorinMathcad;

itstatesthatthevariableontheleftisassignedthevalueorexpressionontheright.Youcannotdefineanexpressionontherightsideofthisoperator;

14:

=sin（x）willproduceanerror.

Sometypicaluses:

Trytheassignmentoperatorbytypingx:

12.5andobservetheresult.Commonmathematicalfunctionscanbefoundbyusingthefunctionicon,f（x）onthetoolbar.Trydefininganewvariabletobethecosineofyandsetyequalto15.

Toevaluateanexpression,usethe“normal”equalssignjustasyouwouldinnormalmathematics.

Noticethatthefunctionisalwaysontheleftsideoftheassignmentoperator.Anexpressionsuchas

makesnosensetoMathcad.

Exercise:

Defineavariabletorepresentthedistanceasafunctionoftime.Thedistancefollowsthisexpression:

initial_position+11.5*time+1.2*time2.

Settheinitialpositionto255andcalculatethepositionattime=2,12,25.

Harmonicmotionfollowsasinusoidalpattern:

position=amplitude*sin（time）+phase.

Defineavariabletorepresentthepositionasafunctionoftimewhentheamplitudeis1.5andthephaseiszero.Calculatethepositionattime=0,12,24,44.

Whatchangetopositionoccursifthephasechanges?

ImportantWarningaboutTypicalScientificSymbols

Mathcadhasabuilt-insetofunitsthatareusedforcancellationandobtainingtheunitsofananswer.Thisisaverypowerfulconceptbutsometimestheseunitscancauseconfusionwhenyoutrytomakethemvariables.Acommonexampleisg.Weallliketousegforgrams,butMathcadhasalreadydefinedthissymbolastheaccelerationduetogravity:

ThisproblemalsooccursforT.WeliketouseTfortemperature,butitrepresentsTesla,thebuilt-inunitformagneticfluxdensity.YoucanuseTinthismanner:

T=325K,whereKisthesymbolforkelvintemperature.Anotherproblemexistsforthelettere.WetypicallyuseeasthechargeonanelectronbutinMathcad,erepresentsthebaseofnaturallogarithms（e=2.781828….）.Mathcadalsowriteseasexpasinex=exp（x）.

SelectingandEditing

Mathcadexpressionscanbeeditedusingthestandardwindowsmethodsforcut,copy,andpaste.Beforeeditingpartofanexpression,theappropriatesectionmustbeselected.Toselectanarea,clickinsidetheexpression;

theredcrosshairwillbecomeablueselectioncursorthatlookslike,or.Thesmall“foot”onthecursorindicateswhichwaythedatawillbeselected.willselecttotheright,whilewillselecttotheleft.Usetheinsertkeytochangethedirection.Thespacebarrepeatedlyexpandstheselection,andtheandkeysmoveitrightandleftrespectively.Tryitonanexpressiontoseehowthesekeyswork

Thespacebarchangestheselectionbypartsofanexpression（piecesconnectedby+,–,*,/）,whilethearrowsmovecharacterbycharacter.Itiseasiertoobservethantoexplain.Buildandexpressionsuchas

andtryit.

Onceapartofanexpressionisselected,youcancutit,deleteit,orcopyit.Youcanalsoedititbysubstitutingdifferentoperators.Textiseditedinthesamemanner.AnyselecteditemcanbepastedintoanotherdocumentsuchasaWorddocumentoranExcelspreadsheet.AlloftheMathcadworkinthisprimerwaspasteddirectlyfromMathcadintoWord.

VariableNames

Mathcadallowsalmostanynameforavariableaslongasthenameisnotapredefinedfunction.Someexamplevariablesare:

Variablenamescanbeanycombinationofalphanumericcharacters.Thesenamesshouldbeginwithaletterandshouldnotcontainsymbolsexceptfortheunderscore（_）,percent（%）,oraprime（`）.Youcannotuseunitsymbolsorbuilt-infunctionsasnames（toseealistofbuilt-infunctions,clickthef（x）onthetoolbar）.Someexamplesofvariablesare:

This_is_a_variableokay

Mass_protonokay

Variable_4okay

Vokay

1st_valueinvalid;

beginswithanumber.

Sin（X）invalid;

sinisabuilt-infunction.

Alistofpredefinedfunctionscanbefoundbyclickingthef（x）icononthetoolbar.

Assimpleexampleofvariables,wecalculatePfromtheidealgaslaw.Definesomevaluesandevaluatethepressure.

Thevariablesaredefinedinthefirstline;

Pisthendefined（asnRT/V）andevaluated.Ifanyvariableisleftundefined,theundefinedquantitieswillbeinred（anerror）.Inthisexample,wedeletethedefinitionforV,thereforePcannotbecalculated.

Youcanputasubscriptaspartofavariablenamebyusingtheperiodcharacteronthekeyboard.Ifwetypev.initial（that’svperiodinitial）,weget

inthedocument.Subscriptedvariablenamescanbequiteuseful.

Units

Bydefault,MathcadwillusetheSIunitsystemforallcalculations.YoucanchangethisintheTools,Worksheetoptions,Displaycommand.GototheUnitstabandchooseasystemofunitsorsetittonone.Youenteraunitforanyquantitybymultiplyinganumericalvaluebytheunit.Ifyouwantavolumeof15liters,youtypeV:

15*L.Thepreviousgaslawexample,withunitsis:

MathcadautomaticallycancelsunitsandproducestheresultinPascals（thedefaultSIunitforpressure）.Ifyoupreferadifferentunitfortheresult,clicktheexpressionandablackboxwillappearafterthePaunit.Double-clickthisboxandasetofpossibleunitswillbeshown;

youcanchoosetheunitsyouwant.Herewechangetheanswertoatmospheres.

Aneasywayto