MATLAB数学实验第二版答案胡良剑doc.docx
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MATLAB数学实验第二版答案胡良剑doc
MATLAB数学实验第二版答案(胡良剑)
数学实验答案
Chapter1
Page20,ex1
(5)等于[exp
(1),exp
(2);exp(3),exp(4)]
(7)3=1*3,8=2*4
(8)a为各列最小值,b为最小值所在的行号
(10)1>=4,false,2>=3,false,3>=2,ture,4>=1,ture
(11)答案表明:
编址第2元素满足不等式(30>=20)和编址第4元素满足不等式(40>=10)
(12)答案表明:
编址第2行第1列元素满足不等式(30>=20)和编址第2行第2列元素满足不等式(40>=10)
Page20,ex2
(1)a,b,c的值尽管都是1,但数据类型分别为数值,字符,逻辑,注意a与c相等,但他们不等于b
(2)double(fun)输出的分别是字符a,b,s,(,x,)的ASCII码
Page20,ex3
>>r=2;p=0.5;n=12;
>>T=log(r)/n/log(1+0.01*p)
Page20,ex4
>>x=-2:
0.05:
2;f=x.^4-2.^x;
>>x(x2_index)
ans=
1.2500
Page20,ex5
>>z=magic(10)
z=
929918156774515840
9880714167355576441
4818820225456637047
8587192136062697128
869325296168755234
17247683904249263365
2358289914830323966
7961395972931384572
10129496783537444653
111810077843643502759
>>sum(z)
>>sum(diag(z))
>>z(:
2)/sqrt(3)
>>z(8,:
)=z(8,:
)+z(3,:
)
Chapter2
Page45ex1
先在编辑器窗口写下列M函数,保存为eg2_1.m
function[xbar,s]=ex2_1(x)
n=length(x);
xbar=sum(x)/n;
s=sqrt((sum(x.^2)-n*xbar^2)/(n-1));
例如
>>x=[81706551766690876177];
>>[xbar,s]=ex2_1(x)
Page45ex2
s=log
(1);n=0;
whiles<=100
n=n+1;
s=s+log(1+n);
end
m=n
Page40ex3
clear;
F
(1)=1;F
(2)=1;k=2;x=0;
e=1e-8;a=(1+sqrt(5))/2;
whileabs(x-a)>e
k=k+1;F(k)=F(k-1)+F(k-2);x=F(k)/F(k-1);
end
a,x,k
计算至k=21可满足精度
Page45ex4
clear;tic;s=0;
fori=1:
1000000
s=s+sqrt(3)/2^i;
end
s,toc
tic;s=0;i=1;
whilei<=1000000
s=s+sqrt(3)/2^i;i=i+1;
end
s,toc
tic;s=0;
i=1:
1000000;
s=sqrt(3)*sum(1./2.^i);
s,toc
Page45ex5
t=0:
24;
c=[15141414141516182022232528...
313231292725242220181716];
plot(t,c)
Page45ex6
(1)
x=-2:
0.1:
2;y=x.^2.*sin(x.^2-x-2);plot(x,y)
y=inline('x^2*sin(x^2-x-2)');fplot(y,[-22])
(2)参数方法
t=linspace(0,2*pi,100);
x=2*cos(t);y=3*sin(t);plot(x,y)
(3)
x=-3:
0.1:
3;y=x;
[x,y]=meshgrid(x,y);
z=x.^2+y.^2;
surf(x,y,z)
(4)
x=-3:
0.1:
3;y=-3:
0.1:
13;
[x,y]=meshgrid(x,y);
z=x.^4+3*x.^2+y.^2-2*x-2*y-2*x.^2.*y+6;
surf(x,y,z)
(5)
t=0:
0.01:
2*pi;
x=sin(t);y=cos(t);z=cos(2*t);
plot3(x,y,z)
(6)
theta=linspace(0,2*pi,50);fai=linspace(0,pi/2,20);
[theta,fai]=meshgrid(theta,fai);
x=2*sin(fai).*cos(theta);
y=2*sin(fai).*sin(theta);z=2*cos(fai);
surf(x,y,z)
(7)
x=linspace(0,pi,100);
y1=sin(x);y2=sin(x).*sin(10*x);y3=-sin(x);
plot(x,y1,x,y2,x,y3)
page45,ex7
x=-1.5:
0.05:
1.5;
y=1.1*(x>1.1)+x.*(x<=1.1).*(x>=-1.1)-1.1*(x<-1.1);
plot(x,y)
page45,ex9
clear;close;
x=-2:
0.1:
2;y=x;
[x,y]=meshgrid(x,y);
a=0.5457;b=0.7575;
p=a*exp(-0.75*y.^2-3.75*x.^2-1.5*x).*(x+y>1);
p=p+b*exp(-y.^2-6*x.^2).*(x+y>-1).*(x+y<=1);
p=p+a*exp(-0.75*y.^2-3.75*x.^2+1.5*x).*(x+y<=-1);
mesh(x,y,p)
page45,ex10
lookforlyapunov
helplyap
>>A=[123;456;780];C=[2-5-22;-5-24-56;-22-56-16];
>>X=lyap(A,C)
X=
1.0000-1.0000-0.0000
-1.00002.00001.0000
-0.00001.00007.0000
Chapter3
Page65Ex1
>>a=[1,2,3];b=[2,4,3];a./b,a.\b,a/b,a\b
ans=
0.50000.50001.0000
ans=
221
ans=
0.6552一元方程组x[2,4,3]=[1,2,3]的近似解
ans=
000
000
0.66671.33331.0000
矩阵方程[1,2,3][x11,x12,x13;x21,x22,x23;x31,x32,x33]=[2,4,3]的特解
Page65Ex2
(1)
>>A=[41-1;32-6;1-53];b=[9;-2;1];
>>rank(A),rank([A,b])[A,b]为增广矩阵
ans=
3
ans=
3可见方程组唯一解
>>x=A\b
x=
2.3830
1.4894
2.0213
(2)
>>A=[4-33;32-6;1-53];b=[-1;-2;1];
>>rank(A),rank([A,b])
ans=
3
ans=
3可见方程组唯一解
>>x=A\b
x=
-0.4706
-0.2941
0
(3)
>>A=[41;32;1-5];b=[1;1;1];
>>rank(A),rank([A,b])
ans=
2
ans=
3可见方程组无解
>>x=A\b
x=
0.3311
-0.1219最小二乘近似解
(4)
>>a=[2,1,-1,1;1,2,1,-1;1,1,2,1];b=[123]';%注意b的写法
>>rank(a),rank([a,b])
ans=
3
ans=
3rank(a)==rank([a,b])<4说明有无穷多解
>>a\b
ans=
1
0
1
0一个特解
Page65Ex3
>>a=[2,1,-1,1;1,2,1,-1;1,1,2,1];b=[1,2,3]';
>>x=null(a),x0=a\b
x=
-0.6255
0.6255
-0.2085
0.4170
x0=
1
0
1
0
通解kx+x0
Page65Ex4
>>x0=[0.20.8]';a=[0.990.05;0.010.95];
>>x1=a*x,x2=a^2*x,x10=a^10*x
>>x=x0;fori=1:
1000,x=a*x;end,x
x=
0.8333
0.1667
>>x0=[0.80.2]';
>>x=x0;fori=1:
1000,x=a*x;end,x
x=
0.8333
0.1667
>>[v,e]=eig(a)
v=
0.9806-0.7071
0.19610.7071
e=
1.00000
00.9400
>>v(:
1)./x
ans=
1.1767
1.1767成比例,说明x是最大特征值对应的特征向量
Page65Ex5
用到公式(3.11)(3.12)
>>B=[6,2,1;2.25,1,0.2;3,0.2,1.8];x=[25520]';
>>C=B/diag(x)
C=
0.24000.40000.0500
0.09000.20000.0100
0.12000.04000.0900
>>A=eye(3,3)-C
A=
0.7600-0.4000-0.0500
-0.09000.8000-0.0100
-0.1200-0.04000.9100
>>D=[171717]';x=A\D
x=
37.5696
25.7862
24.7690
Page65Ex6
(1)
>>a=[41-1;32-6;1-53];det(a),inv(a),[v,d]=eig(a)
ans=
-94
ans=
0.2553-0.02130.0426
0.1596-0.138