matlab中solve函数的用法。悬赏20分

　　solveSymbolicsolutionofalgebraicequations.

　　solve('eqn1','eqn2',...,'eqnN')

　　solve('eqn1','eqn2',...,'eqnN','var1,var2,...,varN')

　　solve('eqn1','eqn2',...,'eqnN','var1','var2',...'varN')

　　Theeqnsaresymbolicexpressionsorstringsspecifyingequations.The

　　varsaresymbolicvariablesorstringsspecifyingtheunknownvariables.

　　solveseekszerosoftheexpressionsorsolutionsoftheequations.

　　Ifnotspecified,theunknownsinthesystemaredeterminedbySYMVAR.

　　Ifnoanalyticalsolutionisfoundandthenumberofequationsequals

　　thenumberofdependentvariables,anumericsolutionisattempted.

　　Threedifferenttypesofoutputarepossible.Foroneequationandone

　　output,theresultingsolutionisreturned,withmultiplesolutionsto

　　anonlinearequationinasymbolicvector.Forseveralequationsand

　　anequalnumberofoutputs,theresultsaresortedinlexicographic

　　orderandassignedtotheoutputs.Forseveralequationsandasingle

　　output,astructurecontainingthesolutionsisreturned.

　　solve(...,'IgnoreAnalyticConstraints',VAL)controlsthelevelof

　　mathematicalrigortouseontheanalyticalconstraintsofthesolution

　　(branchcuts,divisionbyzero,etc).TheoptionsforVALareTRUEor

　　FALSE.SpecifyFALSEtousethehighestlevelofmathematicalrigor

　　infindinganysolutions.ThedefaultisFALSE.

　　solve(...,'PrincipalValue',VAL)controlswhethersolveshouldreturn

　　multiplesolutions,includingparameterizedinfinitesolutionsets

　　(ifVALisFALSE),orjustasinglesolution(whenVALisTRUE).

　　ThedefaultisFALSE.

　　solve(...,'IgnoreProperties',VAL)controlsifsolveshouldtake

　　assumptionsonvariablesintoaccount.VALcanbeTRUEorFALSE.

　　ThedefaultisFALSE(i.e.,takeassumptionsintoaccount).

　　solve(...,'Real',VAL)allowstoputthesolverinto"realmode."

　　In"realmode,"onlyrealsolutionssuchthatallintermediatevalues

　　oftheinputexpressionarerealaresearched.VALcanbeTRUE

　　orFALSE.ThedefaultisFALSE.

　　solve(...,'MaxDegree',n)controlsthemaximumdegreeofpolynomials

　　forwhichexplicitformulaswillbeusedduringthecomputation.

　　nmustbeapositiveintegersmallerthan5.Thedefaultis3.

　　Examples:

　　solve('psin(x)r')chooses'x'astheunknownandreturns

　　ans

　　asin(r/p)

　　pi-asin(r/p)

　　[x,y]solve('x^2+xy+y3','x^2-4x+30')returns

　　x

　　1

　　3

　　y

　　1

　　-3/2

　　Ssolve('x^2y^2-2x-10','x^2-y^2-10')returns

　　thesolutionsinastructure.

　　S

　　x:[8x1sym]

　　y:[8x1sym]

　　[u,v]solve('au^2+v^20','u-v1')regards'a'asa

　　parameterandsolvesthetwoequationsforuandv.

　　Ssolve('au^2+v^2','u-v1','a,u')regards'v'asa

　　parameter,solvesthetwoequations,andreturnsS.aandS.u.

　　[a,u,v]solve('au^2+v^2','u-v1','a^2-5a+6')solves

　　thethreeequationsfora,uandv.

　　Ssolve('x^(5/2)8^(10/3)')returnsallthreecomplexsolutions:

　　S

　　16

　　-45^(1/2)-4+42^(1/2)(5-5^(1/2))^(1/2)i

　　-45^(1/2)-4-42^(1/2)(5-5^(1/2))^(1/2)i

　　Ssolve('x^(5/2)8^(10/3)','PrincipalValue',true)selectsoneofthese:

　　S

　　-45^(1/2)-4+42^(1/2)(5-5^(1/2))^(1/2)i

　　Ssolve('x^(5/2)8^(10/3)','IgnoreAnalyticConstraints',true)

　　ignoresbranchcutsduringinternalsimplificationsand,inthiscase,

　　alsoreturnsonlyonesolution:

　　S

　　16

　　symstpositive

　　solve(t^2-1)

　　ans

　　1

　　solve(t^2-1,'IgnoreProperties',true)

　　ans

　　1

　　-1

　　solve(x^3-1)returnsallthreecomplexroots:

　　ans

　　1

　　-1/2+(3^(1/2)i)/2

　　-1/2-(3^(1/2)i)/2

　　solve(x^3-1,'Real',true)onlyreturnstherealroot:

　　ans

　　1

　　这是具体的用法，注意变量的选取。。。

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