7A文大学MATLAB数学实验第二版答案.docx
《7A文大学MATLAB数学实验第二版答案.docx》由会员分享,可在线阅读,更多相关《7A文大学MATLAB数学实验第二版答案.docx(39页珍藏版)》请在冰豆网上搜索。
7A文大学MATLAB数学实验第二版答案
数学实验答案
Chapter1
Page20,eG1
(5)等于[eGp
(1),eGp
(2);eGp(3),eGp(4)]
(7)3=1G3,8=2G4
(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,eG2
(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,(,G,)的ASCII码
Page20,eG3
>>r=2;p=0.5;n=12;
>>T=log(r)/n/log(1+0.01Gp)
Page20,eG4
>>G=-2:
0.05:
2;f=G.^4-2.^G;
>>[fmin,min_indeG]=min(f)
最小值最小值点编址
>>G(min_indeG)
ans=
0.6500最小值点
>>[f1,G1_indeG]=min(abs(f))求近似根--绝对值最小的点
f1=
0.0328
G1_indeG=
24
>>G(G1_indeG)
ans=
-0.8500
>>G(G1_indeG)=[];f=G.^4-2.^G;删去绝对值最小的点以求函数绝对值次小的点
>>[f2,G2_indeG]=min(abs(f))求另一近似根--函数绝对值次小的点
f2=
0.0630
G2_indeG=
65
>>G(G2_indeG)
ans=
1.2500
Page20,eG5
>>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
Page45eG1
先在编辑器窗口写下列M函数,保存为eg2_1.m
function[Gbar,s]=eG2_1(G)
n=length(G);
Gbar=sum(G)/n;
s=sqrt((sum(G.^2)-nGGbar^2)/(n-1));
例如
>>G=[81706551766690876177];
>>[Gbar,s]=eG2_1(G)
Page45eG2
s=log
(1);n=0;
whiles<=100
n=n+1;
s=s+log(1+n);
end
m=n
Page40eG3
clear;
F
(1)=1;F
(2)=1;k=2;G=0;
e=1e-8;a=(1+sqrt(5))/2;
whileabs(G-a)>e
k=k+1;F(k)=F(k-1)+F(k-2);G=F(k)/F(k-1);
end
a,G,k
计算至k=21可满足精度
Page45eG4
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)Gsum(1./2.^i);
s,toc
Page45eG5
t=0:
24;
c=[15141414141516182022232528...
313231292725242220181716];
plot(t,c)
Page45eG6
(1)
G=-2:
0.1:
2;y=G.^2.Gsin(G.^2-G-2);plot(G,y)
y=inline('G^2Gsin(G^2-G-2)');fplot(y,[-22])
(2)参数方法
t=linspace(0,2Gpi,100);
G=2Gcos(t);y=3Gsin(t);plot(G,y)
(3)
G=-3:
0.1:
3;y=G;
[G,y]=meshgrid(G,y);
z=G.^2+y.^2;
surf(G,y,z)
(4)
G=-3:
0.1:
3;y=-3:
0.1:
13;
[G,y]=meshgrid(G,y);
z=G.^4+3GG.^2+y.^2-2GG-2Gy-2GG.^2.Gy+6;
surf(G,y,z)
(5)
t=0:
0.01:
2Gpi;
G=sin(t);y=cos(t);z=cos(2Gt);
plot3(G,y,z)
(6)
theta=linspace(0,2Gpi,50);fai=linspace(0,pi/2,20);
[theta,fai]=meshgrid(theta,fai);
G=2Gsin(fai).Gcos(theta);
y=2Gsin(fai).Gsin(theta);z=2Gcos(fai);
surf(G,y,z)
(7)
G=linspace(0,pi,100);
y1=sin(G);y2=sin(G).Gsin(10GG);y3=-sin(G);
plot(G,y1,G,y2,G,y3)
page45,eG7
G=-1.5:
0.05:
1.5;
y=1.1G(G>1.1)+G.G(G<=1.1).G(G>=-1.1)-1.1G(G<-1.1);
plot(G,y)
page45,eG9
clear;close;
G=-2:
0.1:
2;y=G;
[G,y]=meshgrid(G,y);
a=0.5457;b=0.7575;
p=aGeGp(-0.75Gy.^2-3.75GG.^2-1.5GG).G(G+y>1);
p=p+bGeGp(-y.^2-6GG.^2).G(G+y>-1).G(G+y<=1);
p=p+aGeGp(-0.75Gy.^2-3.75GG.^2+1.5GG).G(G+y<=-1);
mesh(G,y,p)
page45,eG10
lookforlyapunov
helplyap
>>A=[123;456;780];C=[2-5-22;-5-24-56;-22-56-16];
>>G=lyap(A,C)
G=
1.0000-1.0000-0.0000
-1.00002.00001.0000
-0.00001.00007.0000
Chapter3
Page65EG1
>>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G[2,4,3]=[1,2,3]的近似解
ans=
000
000
0.66671.33331.0000
矩阵方程[1,2,3][G11,G12,G13;G21,G22,G23;G31,G32,G33]=[2,4,3]的特解
Page65EG2
(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
>>G=A\b
G=
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
>>G=A\b
G=
-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
>>G=A\b
G=
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
Page65EG3
>>a=[2,1,-1,1;1,2,1,-1;1,1,2,1];b=[1,2,3]';
>>G=null(a),G0=a\b
G=
-0.6255
0.6255
-0.2085
0.4170
G0=
1
0
1
0
通解kG+G0
Page65EG4
>>G0=[0.20.8]';a=[0.990.05;0.010.95];
>>G1=aGG,G2=a^2GG,G10=a^10GG
>>G=G0;fori=1:
1000,G=aGG;end,G
G=
0.8333
0.1667
>>G0=[0.80.2]';
>>G=G0;fori=1:
1000,G=aGG;end,G
G=
0.8333
0.1667
>>[v,e]=eig(a)
v=
0.9806-0.7071
0.19610.7071
e=
1.00000
00.9400
>>v(:
1)./G
ans=
1.1767
1.1767成比例,说明G是最大特征值对应的特征向量
Page65EG5
用到公式(3.11)(3.12)
>>B=[6,2,1;2.25,1,0.2;3,0.2,1.8];G=[25520]';
>>C=B/diag(G)
C=
0.24000.40000.0500
0.09000.20XX0.0100
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]';G=A\D
G=
37.5696
25.7862
24.7690
Page65EG6
(1)
>>a=[41-1;32-6;1-53];det(a),inv(a),[v,d]=eig(a)
ans=
-94
ans=
0.2553-0.02130.0426
0.1596-0.1383-0.2234
0.1809-0.2234-0.0532
v=
0.0185-0.9009-0.3066
-0.7693-0.1240-0.7248
-0.6386-0.41580.6170
d=
-3.052700
03.67600
008.3766
(2)
>>a=[11-1;02-1;-120];det(a),inv(a),[v,d]=eig(a)
ans=
1
ans=
2.0000-2.00001.0000
1.0000-1.00001.0000
2.0000-3.00002.0000
v=
-0.57730.5774+0.0000i0.5774-0.0000i
-0.57730.57740.5774
-0.57740.5773-0.0000i0.5773+0.0000i
d=
1.000000
01.0000+0.0000i0
001.0000-0.0000i
(3)
>>A=[5765;71087;68109;57910]
A=
5765
71087
68109
57910
>>det(A),inv(A),[v,d]=eig(A)
ans=
1
ans=
68.0000-41.0000-17.000010.0000
-41.000025.000010.0000-6.0000
-17.000010.00005.0000-3.0000
10.0000-6.0000-3.00002.0000
v=
0.83040.09330.39630.3803
-0.5016-0.30170.61490.5286
-0.20860.7603-0.27160.5520
0.1237-0.5676-0.62540.5209
d=
0.0102000
00.843100
003.85810
00030.2887
(4)(以n=5为例)
方法一(三个for)
n=5;
fori=1:
n,a(i,i)=5;end
fori=1:
(n-1),a(i,i+1)=6;end
fori=1:
(n-1),a(i+1,i)=1;end
a
方法二(一个for)
n=5;a=zeros(n,n);
a(1,1:
2)=[56];
fori=2:
(n-1),a(i,[i-1,i,i+1])=[156];end
a(n,[n-1n])=[15];
a
方法三(不用for)
n=5;a=diag(5Gones(n,1));
b=diag(6Gones(n-1,1));
c=diag(ones(n-1,1));
a=a+[zeros(n-1,1),b;zeros(1,n)]+[zeros(1,n);c,zeros(n-1,1)]
下列计算
>>det(a)
ans=
665
>>inv(a)
ans=
0.3173-0.58651.0286-1.62411.9489
-0.09770.4887-0.85711.3534-1.6241
0.0286-0.14290.5429-0.85711.0286
-0.00750.0376-0.14290.4887-0.5865
0.0015-0.00750.0286-0.09770.3173
>>[v,d]=eig(a)
v=
-0.7843-0.7843-0.92370.9860-0.9237
0.5546-0.5546-0.3771-0.00000.3771
-0.2614-0.26140.0000-0.16430.0000
0.0924-0.09240.0628-0.0000-0.0628
-0.0218-0.02180.02570.02740.0257
d=
0.75740000
09.2426000
007.449500
0005.00000
00002.5505
Page65EG7
(1)
>>a=[41-1;32-6;1-53];[v,d]=eig(a)
v=
0.0185-0.9009-0.3066
-0.7693-0.1240-0.7248
-0.6386-0.41580.6170
d=
-3.052700
03.67600
008.3766
>>det(v)
ans=
-0.9255%v行列式正常,特征向量线性相关,可对角化
>>inv(v)GaGv验算
ans=
-3.05270.0000-0.0000
0.00003.6760-0.0000
-0.0000-0.00008.3766
>>[v2,d2]=jordan(a)也可用jordan
v2=
0.07980.00760.9127
0.1886-0.31410.1256
-0.1605-0.26070.4213特征向量不同
d2=
8.376600
0-3.0527-0.0000i0
003.6760+0.0000i
>>v2\aGv2
ans=
8.376600.0000
0.0000-3.05270.0000
0.00000.00003.6760
>>v(:
1)./v2(:
2)对应相同特征值的特征向量成比例
ans=
2.4491
2.4491
2.4491
(2)
>>a=[11-1;02-1;-120];[v,d]=eig(a)
v=
-0.57730.5774+0.0000i0.5774-0.0000i
-0.57730.57740.5774
-0.57740.5773-0.0000i0.5773+0.0000i
d=
1.000000
01.0000+0.0000i0
001.0000-0.0000i
>>det(v)
ans=
-5.0566e-028-5.1918e-017iv的行列式接近0,特征向量线性相关,不可对角化
>>[v,d]=jordan(a)
v=
101
100
1-10
d=
110
011
001jordan标准形不是对角的,所以不可对角化
(3)
>>A=[5765;71087;68109;57910]
A=
5765
71087
68109
57910
>>[v,d]=eig(A)
v=
0.83040.09330.39630.3803
-0.5016-0.30170.61490.5286
-0.20860.7603-0.27160.5520
0.1237-0.5676-0.62540.5209
d=
0.0102000
00.843100
003.85810
00030.2887
>>inv(v)GAGv
ans=
0.01020.0000-0.00000.0000
0.00000.8431-0.0000-0.0000
-0.00000.00003.8581-0.0000
-0.0000-0.0000030.2887
本题用jordan不行,原因未知
(4)
参考6(4)和7
(1)
Page65EGercise8
只有(3)对称,且特征值全部大于零,所以是正定矩阵.
Page65EGercise9
(1)
>>a=[4-313;2-135;1-1-1-1;3-234;7-6-70]
>>rank(a)
ans=
3
>>rank(a(1:
3,:
))
ans=
2
>>rank(a([124],:
))1,2,4行为最大无关组
ans=
3
>>b=a([124],:
)';c=a([35],:
)';
>>b\c线性表示的系数
ans=
0.50005.0000
-0.50001.0000
0-5.0000
Page65EGercise10
>>a=[1-22;-2-24;24-2]
>>[v,d]=eig(a)
v=
0.33330.9339-0.1293
0.6667-0.3304-0.6681
-0.66670.1365-0.7327
d=
-7.000000
02.00000
002.0000
>>v'Gv
ans=
1.00000.00000.0000
0.00001.00000
0.000001.0000v确实是正交矩阵
Page65EGercise11
设经过6个电阻的电流分别为i1,...,i6.列方程组如下
20-2i1=a;5-3i2=c;a-3i3=c;a-4i4=b;c-5i5=b;b-3i6=0;
i1=i3+i4;i5=i2+i3;i6=i4+i5;
计算如下
>>A=[100200000;001030000;10-100-3000;1-10000-400;
0-110000-50;01000000-3;00010-1-100;0000-1-1010;
000000-1-11];
>>b=[2050000000]';A\b
ans=
13.3453
6.4401
8.5420
3.3274
-1.1807
1.6011
1.7263
0.4204
2.1467
Page65EGercise12
>>A=[123;456;780];
>>left=sum(eig(A)),right=sum(trace(A))
left=
6.0000
right=
6
>>left=prod(eig(A)),right=det(A)原题有错,(-1)^n应删去
left=
27.0000
right=
27
>>fA=(A-p
(1)Geye(3,3))G(A-p
(2)Geye(3,3))G(A-p(3)Geye(3,3))
fA=
1.0e-012G
0.08530.14210.0284
0.14210.14210
-0.0568-0.11370.1705
>>norm(fA)f(A)范数接近0
ans=
2.9536e-013
Chapter4
Page84EGercise1
(1)
roots([111])
(2)
roots([30-402-1])
(3)
p=zeros(1,24);
p([1171822])=[5-68-5];
roots(p)
(4)
p1=[23];
p2=conv(p1,p1);
p3=conv(p1,p2);
p3(end)=p3(end)-4;%原p3最后一个分量-4
roots(p3)
Page84EGercise2
fun=inline('GGlog(sqrt(G^2-1)+G)-sqrt(G^2-1)-0.5GG');
fzero(fun,2)
Page84EGercise3
fun=inline('G^4-2^G');
fplot(fun,[-22]);gridon;
fzero(fun,-1),fzero(fun,1),fminbnd(fun,0.5,1.5)
Page84EGercise4
fun=inline('GGsin(1/G)','G');
fplot(fun,[-0.10.1]);
G=zeros(1,10);fori=1:
10,G(i)=fzero(fun,(i-0.5)G0.01);end;
G=[G,-G]
Page84EGercise5
fun=inline('[9GG
(1)^2+36GG
(2)^2+4GG(3)^2-36;G
(1)^2-2GG
(2)^2-20GG(3);16GG
(1)-G
(1)^3-2GG
(2)^2-16GG(3)^2]','G');
[a,b,c]=fsolve(fun,[000])
Page84EGercise6
fun=@(G)[G
(1)-0.7Gsin(G
(1))-0.2Gcos(G
(2)),G
(2)-0.7Gcos(G
(1))+0.2Gsin(G
(2))];
[a,b,c]=fsolve(fun,[0.50.5])
Page84EGercise7
clear;close;t=0:
pi/100:
2Gpi;
G1=2+sqrt(5)Gcos(t);y1=3-2GG1+sqrt(5)Gsin(t);
G2=3+sqrt
(2)Gcos(t);y2=6Gsin(t);
plot(G1,y1,G2,y2);gridon;作图发现4个解的大致位置,然后分别求解
y1=fsolve('[(G
(1)-2)^2+(G
(2)-3+2GG
(1))^2-5,2G(G
(1)-3)^2+(G
(2)/3)^2-4]',[1.5,2])
y2=fsolve('[(G
(1)-2)^2+(G
(2)-