6 MATLAB的符号计算答案.docx
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6MATLAB的符号计算答案
%红色为程序运行结果
%PPT12页练习
symsx;
f=cos(x)+sqrt(-(sin(x))^2);
y1=simplify(f)
y2=simple(f)
y1=cos(x)+(-1+cos(x)^2)^(1/2)
y2=cos(x)+i*sin(x)
%PPT13页例题
symsax;
f=a*sin(x)+5;
f1=subs(f,[a,x],[2,pi/3])
f2=subs(f,sin(x),y)
f1=6.7321
f2=a*y+5
%PPT18页求极限
1
symsx;
f=(1+4*x)^(1/x);
limit(f)
ans=exp(4)
2
symsx;
f=(exp(x)-1)/x;
limit(f)
ans=1
3
symsx;
f=2*sin(x)/(x^3+3*x);
limit(f)
ans=2/3
4
symsx;
f=(sqrt(5*x-4)-sqrt(x))/(x-1);
limit(f,x,1)
ans=2
5
symsx;
f=(1-2/x)^(2*x);
limit(f,x,inf)
ans=exp(-4)
6
symsx;
f=(sin(1/x)+cos(1/x))^x;
limit(f,x,inf)
ans=exp
(1)
%PPT22参数方程例题
symst;
x=log(cos(t));
y=cos(t)-t*sin(t);
y1=diff(y,t)/diff(x,t)
y2=diff(y,t,2)/diff(x,t,2)
t=pi/3;
eval(y2)
y1=-(-2*sin(t)-t*cos(t))/sin(t)*cos(t)
y2=(-3*cos(t)+t*sin(t))/(-1-sin(t)^2/cos(t)^2)
ans=0.1483
%PPT23页求导部分
1
symsx;
f=x^10+10^x+1/log10(x);
y=diff(f)
y=10*x^9+10^x*log(10)-1/log(x)^2*log(10)/x
2
symsx;
f=log(2-x^2);
diff(f,2)
ans=-2/(2-x^2)-4*x^2/(2-x^2)^2
3
symsxy;
f=exp(2*x)*(x+y^2+2*y);
y1=diff(f,x)
y2=diff(f,y)
y1=2*exp(2*x)*(x+y^2+2*y)+exp(2*x)
y2=exp(2*x)*(2*y+2)
4
symsxy;
f=(cos(2*x+y))^2;
y1=diff(f,x,2)
y2=diff(f,y,2)
y1=8*sin(2*x+y)^2-8*cos(2*x+y)^2
y2=2*sin(2*x+y)^2-2*cos(2*x+y)^2
5
symsxy;
s=x^2*sin(y);
y1=diff(f,x)
y2=diff(y1,y)
y1=-4*cos(2*x+y)*sin(2*x+y)
y2=4*sin(2*x+y)^2-4*cos(2*x+y)^2
%PPT26页求不定积分
1
symsx;
f=x^2/sqrt(2-x^2);
y=int(f)
y=-1/2*x*(2-x^2)^(1/2)+asin(1/2*2^(1/2)*x)
2
symsx;
f=sin(2*x)*sin(3*x);
y=int(f)
y=1/2*sin(x)-1/10*sin(5*x)
3
symsabx;
f=1/(x*(log(x)+a+sqrt(log(x)+b)));
y=int(f)
y=
1/2*log(log(x)^2+2*log(x)*a+a^2-log(x)-b)+1/(-4*b-1+4*a)^(1/2)*atan((2*log(x)+2*a-1)/(-4*b-1+4*a)^(1/2))-1/2*log(log(x)+a-(log(x)+b)^(1/2))-1/(-4*b-1+4*a)^(1/2)*atan((2*(log(x)+b)^(1/2)-1)/(-4*b-1+4*a)^(1/2))+1/2*log(log(x)+a+(log(x)+b)^(1/2))-1/(-4*b-1+4*a)^(1/2)*atan((1+2*(log(x)+b)^(1/2))/(-4*b-1+4*a)^(1/2))
4
symsx;
f=[sin(x)x^3;x*exp(x)tan(x)];
y=int(f)
y=[-cos(x),1/4*x^4]
[x*exp(x)-exp(x),-log(cos(x))]
%PPT28页求一元定积分
1
symsx;
f=exp(-x^2);
int(f,x,0,1)
ans=1/2*erf
(1)*pi^(1/2)
2
symst;
f=(t^2+4)/(t^2+2);
int(f,t,0,2)
ans=2+2^(1/2)*atan(2^(1/2))
3
symsx;
f=sqrt((sin(x))^3-(sin(x))^5);
int(f,x,0,pi)
ans=1/5*2^(1/2)*8^(1/2)
4
symsx;
f=1/(1+8*(sin(x))^2);
int(f,x,0,pi/6)
ans=-1/3*atan(cot(5/12*pi)/(2*2^(1/2)-3))+1/3*atan(cot(5/12*pi)/(3+2*2^(1/2)))
5
symsxt;
f=exp(-5*x)*sin(3*x+pi/3);
p=subs(f,x,t+x);
y=f*p;
int(y,0,t)
ans=
1/17680*(100*sin(t)*3^(1/2)-7800*sin(t)*cos(t)^2+402*cos(t)+195*sin(t)+1700*sin(t)^3*cos(t)^2*3^(1/2)-41600*cos(t)^9+93600*cos(t)^7+11310*cos(t)^3*3^(1/2)-76300*sin(t)*3^(1/2)*cos(t)^4+145600*sin(t)*3^(1/2)*cos(t)^6+10875*sin(t)*cos(t)^2*3^(1/2)+10920*sin(t)^2*3^(1/2)*cos(t)^3-31200*sin(t)^2*3^(1/2)*cos(t)^5-1170*sin(t)^2*3^(1/2)*cos(t)+24960*sin(t)^2*cos(t)^7*3^(1/2)+1300*exp(t)^10*sin(t)*cos(t)^2*3^(1/2)+41600*cos(t)^7*sin(t)^2-52000*sin(t)^2*cos(t)^5-780*exp(t)^10*sin(t)*cos(t)^2-585*exp(t)^10*cos(t)*3^(1/2)-325*exp(t)^10*sin(t)*3^(1/2)+780*exp(t)^10*cos(t)^3*3^(1/2)-585*cos(t)*3^(1/2)-675*cos(t)*sin(t)^2+16500*cos(t)^3*sin(t)^2-71900*cos(t)^5+18289*cos(t)^3+46800*cos(t)^4*sin(t)-24960*3^(1/2)*cos(t)^9-87360*cos(t)^6*sin(t)+49920*cos(t)^8*sin(t)+56160*3^(1/2)*cos(t)^7-42120*3^(1/2)*cos(t)^5-425*sin(t)^3*3^(1/2)-83200*sin(t)*cos(t)^8*3^(1/2)+4836*exp(t)^10*cos(t)^3-3627*exp(t)^10*cos(t)+195*exp(t)^10*sin(t))/exp(t)^15
%PPT31页多重积分运算
1
symsxy;
f=x^2*exp(-y^2);
int(int(f,x,0,y),y,0,1)
ans=-1/3*exp(-1)+1/6
2
symsxy;
iy=int(sqrt(1-x^2),y,-sqrt(1-x^2),sqrt(1-x^2));
int(iy,x,-1,1)
ans=8/3
%PPT34页多重积分运算
1
symst;
t=0:
0.1:
10;
y=exp(-0.8.*t.*abs(sin(t)));
s1=trapz(t,y)
ff=inline('exp(-0.8.*t.*abs(sin(t)))');
s2=quad(ff,0,10)
s1=2.6576
s2=2.6597
2
symsx;
x=exp
(1):
0.1:
6;
y=x.^2.*log(x);
s1=trapz(x,y)
ff=inline('x.^2.*log(x)');
s2=quad(ff,exp
(1),6)
s1=95.3790
s2=100.5432
3
symsx;
x=0:
pi/12:
pi;
y=sqrt(sin(x)-(sin(x)).^3);
ff=inline('sqrt(sin(x)-(sin(x)).^3)');
s1=trapz(x,y)
s2=quad(ff,0,pi)
s1=1.2661
s2=1.3333
4
symsx;
x=-1:
0.1:
1;
y=exp(-x.^2);
ff=inline('exp(-x.^2)');
s1=trapz(x,y)
s2=quad(ff,-1,1)
s1=1.4924
s2=1.4936
%PPT35页多重积分运算
1
symsxy;
ff=inline('x.^2+y');
q=dblquad(ff,0,1,0,1)
q=0.8333
2
symsxy;
ff=inline('y.^2./x.^2');
q=dblquad(ff,1/2,2,1,2)
q=3.5000
3
symsrtheda;
ff=inline('sqrt(1+r.*sin(theda))');
q=dblquad(ff,0,1,0,pi)
q=3.5909
%PPT39页多重积分运算
1、
symsxn;
f1=(1+x/n)^n;
f2=(-1)^n*x^n/n;
f3=sin(x*y);
s1=limit(f1,n,inf)
s2=symsum(f2,1,inf)
s3=diff(f3,x,2)
s1=exp(x)
s2=sum((-1)^n*x^n/n,x=1..Inf)
s3=-sin(x*y)*y^2
2
symsx;
f=sin(x);
s=taylor(f,6,x,0)
s=x-1/6*x^3+1/120*x^5
3
(1)
symsnk;
f=1/((5*k-4)*(5*k+1));
s1=symsum(f,k,1,n)
s2=symsum(f,k,1,inf)
s1=-1/5/(5*n+1)+1/5
s2=1/5
3
(2)
symsnk;
f=1/2^k+1/3^k;
s1=symsum(f,k,1,n)
s2=symsum(f,k,1,inf)
s1=-2*(1/2)^(n+1)-3/2*(1/3)^(n+1)+3/2
s2=3/2
4
(1)
symsnk;
f=1/((2*k)^2-1);
f1=symsum(f,k,1,n);
s=limit(f1,n,inf)
s=1/2
4
(2)
symsnk;
f=1/(n^2+k*pi);
f1=symsum(f,k,1,n);
s=limit(n*f1,n,inf)
s=1
%PPT43页例题
ff=inline('x
(1)^4+sin(x
(2))-cos(x(3))');
x0=[054];
[x,fval]=fminsearch(ff,x0)
x=-0.00214.71246.2832
fval=-2.0000
%PPT45页练习
x1=fzero('x^4-4*x-5',-5)%第
(1)题
x2=fzero('sin(3*x)',2)%第
(2)题
x3=fzero('sin(x)-log(x+0.1)',1)%第(3)题
x1=-1
x2=2.0944
x3=NaN
%PPT45页练习
(1)
symsxab;
s=x^2-a*x-4*b;
solve(s)
ans=1/2*a+1/2*(a^2+16*b)^(1/2)
1/2*a-1/2*(a^2+16*b)^(1/2)
(2)
solve(sym(x^9-x^8+1))
ans=
1.1228174396026853653525590840144+.28363052586617358353928597350912*i
.60944290027631923574927798035197+.80967283242662774065903710738338*i
-.85784190205533577358632528477576e-1+.95128761278822288069698079288831*i
-.68567648985647952059348937828781+.62718337618433236630566609958131*i
-.92159931963398300629943031520197
-.68567648985647952059348937828781-.62718337618433236630566609958131*i
-.85784190205533577358632528477576e-1-.95128761278822288069698079288831*i
.60944290027631923574927798035197-.80967283242662774065903710738338*i
1.1228174396026853653525590840144-.28363052586617358353928597350912*i
(3)
solve(sym(x^6-x^2+2*x-3))
ans=
1.1238932511762955476010811097327
.60804677070454177795683814517971+.88541124247455434577495883624571*i
-.46586916707607665574895492689981+1.1941322239415680694023931300200*i
-1.4082484584332257920168475462925
-.46586916707607665574895492689981-1.1941322239415680694023931300200*i
.60804677070454177795683814517971-.88541124247455434577495883624571*i
%PPT50页练习
(1)
(2)
x1=solve('x^2+b*x+c=0')%第
(1)题
x2=solve('a*x^2-b*x-6=0')%第
(2)题
x2=1/2/a*(b+(b^2+24*a)^(1/2))
1/2/a*(b-(b^2+24*a)^(1/2))
(3)(4)
[x3,y3]=solve('x+y=1','x-11*y=5','x','y')%第(3)题
[x4,y4]=solve('x+3*y=1','x^2+y^2=1','x','y')%第(4)题
x3=4/3y3=-1/3
x4=1-4/5
y4=03/5
%PPT52页练习
1
ff=inline('[x
(1)-x
(2)^2,x
(2)-cos(x
(1))]','x');
f=fsolve(ff,[1,2])
f=0.64170.8011
2
ff=inline('[sin(x
(1))+x
(2)^2+log(x(3))-7,3*x
(1)+x
(2)^2-x(3)^3+1,x
(1)+x
(2)+x(3)]','x');
f=fsolve(ff,[1,1,1])
f=-3.14202.90510.2370
%PPT57页练习
s1=dsolve('Dy=x*sin(x)/cos(y)','x')%第
(1)题
s2=dsolve('D2y+4*Dy+29*y=0','y(0)=0','Dy(0)=15','x')%第
(2)题
%第(3)题
[x,y,z]=dsolve('Dx=2*x-3*y+3*z','Dy=4*x-5*y+3*z','Dz=4*x-4*y+2*z','t');
x=simple(x)
y=simple(y)
z=simple(z)
s1=-asin(-sin(x)+x*cos(x)-C1)
s2=3*exp(-2*x)*sin(5*x)
x=C2*exp(t)^2+C3/exp(t)
y=C3*exp(-t)+C2*exp(2*t)+exp(-2*t)*C1
z=C2*exp(2*t)+exp(-2*t)*C1
s4=dsolve('x*Dy=y*log(x*y)-y','x')%第(4)题
s5=dsolve('Dv+2*t=0','v
(1)=5','t')%第(5)题
s6=dsolve('D2y-(a+b)*Dy+a*b*y=0')%第(6)题
s7=dsolve('D2y=x*sin(x)','y(0)=1/2','Dy
(2)=0','x')%第(7)题
s4=exp(x/C1)/x
s5=-t^2+6
s6=C1*exp(b*t)+C2*exp(a*t)
s7=-2*cos(x)-x*sin(x)+(-sin
(2)+2*cos
(2))*x+5/2
%PPT61页练习
1
ezplot('sin(x)',[0,pi])
2
ezplot('(cos(t))^3','(sin(t))^3',[0,2*pi])
3
ezplot('exp(x)+sin(x*y)',[-2,0.5,0,2])