matlab张志涌版课后习题答案 matlab教程(张志涌)课后习题答案.doc

matlab教程(张志涌)课后习题答案

matlab教程(张志涌)课后习题答案

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第二章

%分段函数的写法

syms y x

z=int(x*y,x,0,1);

g = evalin(symengine,[‘ piecewise([y > 1/2,’ char(z) ‘], [y <= 1/2, 1])’])

G=int(g,y)

g =

piecewise([1/2 < y, y/2], [y <= 1/2, 1])

G =

piecewise([1/2 < y, y/4], [y <= 1/2, y])

%习题2-1

class(vpa(sym(3/7+0.1),4))

%习题2-2

findsym(sym(‘sin(w*t)’),1)

findsym(sym(‘a*exp(-X)’),1)

findsym(sym(‘z*exp(j*th)’),1)

%习题2-3

syms x a positive

x_,0,inf)

s1=simple(s)

%习题2-8

clear all, syms t

y=abs(sin(t))

df=diff(y),class(df)

df1=limit(df,t,0,’left’)

df2=subs(df,’t’,sym(pi/2))

%习题2-9

clear all, syms x;

f=exp(-abs(x)).*abs(sin(x));

fint=int(f,x,-5*pi,1.7*pi), digits(64), vpa(fint)

class(fint)

%习题2-10

clear all,syms x y,f=x.+y.,

fint=(int(int(f,y,1,x.),x,1,2)), double(fint)

%习题2-11

clear all, syms t x; f=sin(t)/t, yx=int(f,t,0,x), ezplot(yx,[0 2*pi])

fint=subs(yx,x,4.5),%或yxd=int(f,t,0,4.5),fint=double(yxd)

hold on, plot(4.5,fint,’*r’)

%习题2-12

% clear all, syms x n; f=(sin(x)); yn=int(f,’x’,0,pi/2), class(yn)

clear all, syms x n; syms n positive ; f=(sin(x)); yn=int(f,’x’,0,pi/2), class(yn)

% y(1/3)=?

yn1=subs(yn,’n’,sym(1/3)gure

plot(t,subs(S1,x,t)), hold on

plot(t,subs(S2,x,t))

axis([-2,2 -2,2])

%习题2-24

x=dsolve(‘Dx=a*t+b*t’,’x(0)=2’,’t’)

%习题2-25

[f,g]=dsolve(‘Df=3*f+4*g’,’Dg=-

4*f+3*g’,’f(0)=0’,’g(0)=1’,’x’)

第三章

%习题3-1

a=0:2*pi/9:2*pi

b=linspace(0,2*pi,10)

%习题3-2

rand( ‘twister’,0),

A=rand(3,5)

[I1,J1]=find(A>0.5)

subindex_A=sub2ind(size(A),I1,J1)

subindex_A=find(A>0.5)

[I,J]=ind2sub(size(A),subindex_A)

index_A=[I J]

%122_2

rand(‘twister’,0),A=rand(3,5),B=A>0.5,C=find(B)

[ci,cj]=ind2sub(size(A),C) %此法太繁

[Ci,Cj]=find(B)

%122_5

t=linspace(1,10,100)

(1) y=1-exp(-0.5.*t).*cos(2.*t),plot(t,y)

(2) L=length(t)

for k=1:L, yy(k)=1-exp(-0.5*t(k))*cos(2*t(k)), end, plot(t,yy)

%122_6

clear,format long, rand(‘twister’,1),A=rand(3,3),

B=diag(diag(A)),C=A.*(~B)%或C=A-B%或C=triu(A,1)+tril(A,-1)

%习题3-3

% s=sign(randint(1,1000,[],