1第2章符号扑?2.1符号对象和符号表达式2.1.1符号对象的创建和衍生1生成符号对象的基本规则2符号数字和符号常数【例2.1-1】a=pi+sqrt(5)sa=sym('pi+sqrt(5)')Ca=class(a)Csa=class(sa)vpa(sa-a)a=5.3777sa=pi+5^(1/2)Ca=doubleCsa=symans=0.0000000000000000138223758410852000485935425641883基本符号变量4自由符号变量【例2.1-2】。（1）symsuvwza5f=sym('3');Eq=sin(f)*u*z^2+v*z+f*w-a5;（2）symvar(Eq)ans=[a5,u,v,w,z]symvar(Eq,100)ans=[w,z,v,u,a5]symvar(Eq,1)ans=w（3）result_1=solve(Eq)2result_1=a5/3-(v*z)/3-(u*sin(3)*z^2)/3（4）result_2=solve(Eq,z)result_2=-(v-(v^2+4*a5*u*sin(3)-12*u*w*sin(3))^(1/2))/(2*u*sin(3))-(v+(v^2+4*a5*u*sin(3)-12*u*w*sin(3))^(1/2))/(2*u*sin(3))【例2.1-3】（1）symsabxXYk=sym('3');z=sym('c*sqrt(d)+y*sin(t)');EXPR=a*z*X+(b*x^2+k)*Y;（2）symvar(EXPR)ans=[X,Y,a,b,c,d,t,x,y]（3）symvar(EXPR,10)ans=[x,y,t,d,c,b,a,X,Y]（4）symvar(EXPR,1)ans=x（5）symvar(EXPR,3)ans=[x,y,t]（6）E3=sym('a*sqrt(theta)')???Errorusing==>sym.sym>sym.sym/scalarsymat382Error:argumentmustbeof'Type::Arithmetical'[sqrt]Errorin==>sym.sym>sym.sym/char2symat337Scell=scalarsym(x);Errorin==>sym.sym>sym.sym/symcharat182Scell=char2sym(x);Errorin==>sym.sym>sym.symat120S=cell2sym(S,symchar(x,a,nargin));E4=sym('a*sqrt(theta123)')E4=a*theta123^(1/2)E5=sym('a*sqrt(theta*t)')E5=a*(t*theta)^(1/2)3【例2.1-4】symsabtuvxyA=[a+b*x,sin(t)+u;x*exp(-t),log(y)+v]symvar(A,1)A=[a+b*x,u+sin(t)][x/exp(t),v+log(y)]ans=x2.1.2符号计算中的算符2.1.3符号计算中的函数指令2.1.4符号对象的识别【例2.1-5】。（1）cleara=1;b=2;c=3;d=4;Mn=[a,b;c,d]Mc='[a,b;c,d]'Ms=sym(Mc)Mn=1234Mc=[a,b;c,d]Ms=[a,b][c,d]（2）SizeMn=size(Mn)SizeMc=size(Mc)SizeMs=size(Ms)SizeMn=22SizeMc=19SizeMs=22（3）CMn=class(Mn)CMc=class(Mc)CMs=class(Ms)CMn=doubleCMc=charCMs=sym4（4）isa(Mn,'double')isa(Mc,'char')isa(Ms,'sym')ans=1ans=1ans=1（5）w