matlab课后习题答案 附图文档格式.docx
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(1)
symsn
limit((n^3+3^n)^(1/n))
ans=
3
(2)
symsn
limit((n+2)^(1/2)-2*(n+1)^(1/2)+n^(1/2),n,inf)
0
(3)
symsx;
limit(x*cot(2*x),x,0)
1/2
(4)
symsxm;
limit((cos(m/x))^x,x,inf)
1
(5)
symsx
limit(1/x-1/(exp(x)-1),x,1)
(exp
(1)-2)/(exp
(1)-1)
(6)
limit((x^2+x)^(1/2)-x,x,inf)
练习2.4
1.求下列不定积分,并用diff验证:
Clear
symsxy
y=1/(1+cos(x));
f=int(y,x)
f=
tan(1/2*x)
y=tan(1/2*x);
yx=diff(y,x);
y1=simple(yx)
y1=
1/2+1/2*tan(1/2*x)^2
symsxy
y=1/(1+exp(x));
f=int(y,x)
f=
-log(1+exp(x))+log(exp(x))
y=-log(1+exp(x))+log(exp(x));
yx=diff(y,x);
y1=simple(yx)
y1=
1/(1+exp(x))
y=x*sin(x)^2;
f=int(y,x)
f=
x*(-1/2*cos(x)*sin(x)+1/2*x)-1/4*cos(x)^2-1/4*x^2
symsxyy=x*(-1/2*cos(x)*sin(x)+1/2*x)-1/4*cos(x)^2-1/4*x^2;
y1=simple(yx)
y1=
x*sin(x)^2
(4)
y=sec(x)^3;
1/2/cos(x)^2*sin(x)+1/2*log(sec(x)+tan(x))
y=1/2/cos(x)^2*sin(x)+1/2*log(sec(x)+tan(x));
1/cos(x)^3
2.求下列积分的数值解
1)
y=int(x^(-x),x,0,1)
y=
int(x^(-x),x=0..1)
vpa(y,10)
1.291285997
2)
clear
y=int(exp(2*x)*cos(x)^3,x,clear
y=int((1/(2*pi)^(1/2))*exp(-x^2/2),x,0,1)
y=
7186705221432913/36028797018963968*erf(1/2*2^(1/2))*2^(1/2)*pi^(1/0,2*pi)
22/65*exp(pi)^4-22/65vpa(ans,10)
(3)
symsx
y=int(1/(2*pi)^(1/2)*exp(-x^2/2),0,1);
vpa(y,14)
.34134474606855
2(4)
y=int(x*log(x^4)*asin(1/x^2),1,3);
Warning:
Explicitintegralcouldnotbefound.
Insym.intat58
2.4597721282375
2(5)
y=int(1/(2*pi)^(1/2)*exp(-x^2/2),-inf,inf);
.99999999999999
练习2.5
1判断下列级数的收敛性,若收敛,求出其收敛值。
1)symsn
s1=symsum(1/n^(2^n),n,1,inf)
s1=
sum(1/(n^(2^n)),n=1..Inf)
vpa(s1,10)
ans=
1.062652416
因此不收敛
2)symsn
s1=symsum(sin(1/n),n,1,inf)
s1=
sum(sin(1/n),n=1..Inf)
vpa(s1,10)
不收敛
(3)
symsn
s=symsum(log(n)/n^3,n,1,inf)
s=
-zeta(1,3)
收敛
(4)symsn
s1=symsum(1/(log10(n))^n,n,3,inf)
sum(1/((log(n)/log(10))^n),n=3..inf)
(5)symsn
s1=symsum(1/n*log10(n),n,2,inf)
sum(1/n*log(n)/log(10),n=2..Inf)
(6)
s=symsum((-1)^n*n/n^2+1,n,1,inf)
sum((-1)^n/n+1,n=1..Inf)
习题3.1
1)clear;
[x,y]=meshgrid(-30:
0.3:
30);
z=10*sin(sqrt(x.^2+y.^2))./sqrt(1+x.^2+y.^2);
meshc(x,y,z)
[x,y]=meshgrid(-30:
z=10*sin((x^2+y^2)^(1/2))/(1+x^2+y^2)^(1/2)
mesh(x,y,z)
1.
2.取适当的参数绘制下列曲面的图形。
a=-2:
2;
b=-3:
3;
[x,y]=meshgrid(a,b);
z=(1-(x.^2)/4-(y.^2)/9).^(1/2);
mesh(x,y,z)
holdon
mesh(x,y,-z)
a=-1:
1;
b=-2:
[x,y]=meshgrid(a,b);
z=(4/9)*(x.^2)+(y.^2);
[x,y]=meshgrid(-1:
1);
z=(1/3)*(x.^2)-(1/3)*(y.^2);
习题3.2
P49/例3.2.1
命令:
limit(limit((x^2+y^2)/(sin(x)+cos(y)),0),pi),
-pi^2
limit(limit((1-cos(x^2+y^2))/((x^2+y^2)),0),0),
P49/例3.2.2
clear;
symsxyzdxdydzzxzzyzxxzxy
z=atan(x^2*y)
z=
atan(x^2*y)
zx=diff(z,x),zy=diff(z,y)
zx
2*x*y/(1+x^4*y^2)
zy=
x^2/(1+x^4*y^2)
dz=zx*dx+zy*dy,
dz=
2*x*y/(1+x^4*y^2)*dx+x^2/(1+x^4*y^2)*d
zxx=diff(zx,x),zxy=diff(zx,y)
zxx=
2*y/(1+x^4*y^2)-8*x^4*y^3/(1+x^4*y^2)^2
zxy=
2*x/(1+x^4*y^2)-4*x^5*y^2/(1+x^4*y^2)^2
3.2.1作图表示函数z=x*exp(-x^2-y^2)(-1<
x<
1,0<
y<
2)沿x轴方向梯度
b=0:
z=x.*exp(-x.^2-y.^2);
[px,py]=gradient(z,0.1,0.1);
contour(a,b,z),holdon,
quiver(a,b,px,py),holdoff
习题3.4
1.解下列微分方程
(1)y=dsolve('
Dy=x+y'
'
y(0)=1'
x'
-x-1+2*exp(x)
x=[123]
x=123
-x-1+2*exp(x)
3.436611.778136.1711
(2)x'
=2*x+3*y,y'
=2*x+y,x(0)=-2,y(0)=2.8,0<
t<
10,做相平面图
新建M函数
functiondy=weifen1(t,y)
dy=zeros(2,1);
dy
(1)=2*y
(1)+3*y
(2);
dy
(2)=2*y
(1)+y
(2);
输入命令
10;
[t,y]=ode15s('
weifen1'
[0,10],[-22.8]);
plot(t,y)
(3)y'
'
-0.01(y'
)^2+2*y1=sin(t),y(0)=0,y'
(0)=1,0<
5,做y的图
functiondy=weifen2(t,y)
dy
(1)=y
(2);
dy
(2)=0.01*y
(2)^2-2*y
(1)+sin(t);
weifen2'
[0,5],[01]);
1.绘制飞船轨迹图
functiondy=weifen3(t,y)
dy=zeros(4,1);
dy
(1)=y(3);
dy
(2)=y(4);
dy(3)=2*y(4)+y
(1)-(1-1/82.45)*(y
(1)+1/82.45)/((y
(1)+1/82.45)^2+y
(2)^2)^(3/2)-(1/82.45)*(y
(1)+1/82.45-1)/((y
(1)+1-1/82.45)^2+y
(2)^2)^(3/2);
dy(4)=-2*y(3)+y
(2)-(1-1/82.45)*y
(2)^2/((y
(1)+1/82.45)^2+y
(2)^2)^(3/2)-(1/82.45)*y
(2)/((y
(1)+1-1/82.45)^2+y
(2)^2)^(3/2);
weifen3'
[0,10],[1.200-1]);
习题4.1
4.1.5
(1)>
p=[101];
q=[10001];
[a,b,r]=residue(p,q)
a=
-0.0000-0.3536i
-0.0000+0.3536i
0.0000-0.3536i
0.0000+0.3536i
b=
-0.7071+0.7071i
-0.7071-0.7071i
0.7071+0.7071i
0.7071-0.7071i
r=
[]
formatrat
a
-1/6369051672525780-1189/3363i
-1/6369051672525779+1189/3363i
1/5095241338020627-1189/3363i
1/5095241338020627+1189/3363i
4.1.5
(2)>
p=[1];
q=[10001];
[a,b,r]=residue(p,q)
0.1768-0.1768i
0.1768+0.1768i
-0.1768-0.1768i
-0.1768+0.1768i
r=
a
1189/6726-1189/6726i
1189/6726+1189/6726i
-1189/6726-1189/6726i
-1189/6726+1189/6726i
习题4.2
4.2.1
(1)
D=[2131;
3-121;
1232;
5062];
det(D)
6
4.3.3
(1)
A=[010;
100;
001];
B=[100;
001;
010];
C=[1-43;
20-1;
1-20];
X=C*inv(A)*inv(B)
X=
-431
0-12
-201
习题4.3
4.3.3
(2)
D=[123;
223;
351];
D1=[123;
D2=[113;
331];
D3=[121;
222;
353];
X1=det(D1)/det(D);
X2=det(D2)/det(D);
X3=det(D3)/det(D);
X1,X2,X3
X1=
1
X2=
0
X3=
4.4.1
(1)
A=[42-1;
3-12;
1130];
B=[42-12;
3-1210;
11308];
rank(A),RANK(B)
2
FunctioncallRANKinvokesinexactmatchE:
\toolbox\matlab\matfun\rank.m.
3
习题4.4
4.4.1(3)
A=[1111;
12-14;
2-3-1-5;
31211];
B=[11115;
12-14-2;
2-3-1-5-2;
312110];
rank(A),rank(B)
4
习题4.5
4.5.1(3)
A=[41-1;
32-6;
1-53];
[a,b]=eig(A)
92/4963-1237/1373-424/1383
-627/815-449/3622-1301/1795
-1122/1757-1097/2638559/906
-4695/153800
01963/5340
008318/993
4.5.1(5)
A=[5765;
71087;
68109;
57910];
431/519308/3301472/1191551/1449
-641/1278-2209/73231175/19112100/3973
-434/20811050/1381-855/3148494/895
368/2975-1049/1848-3157/5048473/908
23/2266000
01639/194400
003615/9370
0002938/97
4.5.3
A=[200;
032;
023];
[a,b]=eig(A);
010
-985/13930985/1393
985/13930985/1393
100
020
005
p=orth(a)
p=
0-10
B=p'
*A*p
B=
100
p*p'
100
001
习题5.7
5.7.5
x=0:
0.01:
y=exp(-x.^2/2);
plot(x,y);
symsx;
vpa(int(exp(-x.^2/2),x,0,1),6)
.855620
n=10000;
x=rand(n,1);
y=rand(n,1);
m=sum(y<
exp(-x.^2/2))
m=
8564
s=m/n
0.8564
练习6.7
求这两家煤场如何分配供煤能使总运输量最小
建立数学模型:
minz=10*x1+5*x2+6*x3+4*x4+8*x5+15*x6
s.t.:
x1+x2+x3>
=60
x4+x5+x6>
=100
x1+x4=45
x2+x5=75
x3+x6=40
c=[10;
5;
6;
4;
8;
15];
A=[-1-1-1000;
000-1-1-1];
b=[-60;
-100];
Aeq=[100100;
010010;
001001];
beq=[45;
75;
40];
lb=zeros(6,1);
[x,fv]=linprog(c,A,b,Aeq,beq,lb)
Optimizationterminated.
x=
0.0000
20.0000
40.0000
45.0000
55.0000
0.0000
fv=
960.0000