matlab-第二章
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第一大题:(1)a = 7/3b = sym(7/3)c = sym(7/3,'d')d = sym('7/3')v1=vpa(abs(a-d))v2=vpa(abs(b-d))v3=vpa(abs(c-d))a =2.3333b =7/3c =2.3333333333333334813630699500209d =7/3v1 =0.0v2 =0.0v3 =0.00000000000000014802973661668756666666667788716(2)a = pi/3b = sym(pi/3)c = sym(pi/3,'d')d = sym('pi/3')v1=vpa(abs(a-d))v2=vpa(abs(b-d))v3=vpa(abs(c-d))a =1.0472b =pi/3c =1.047197551196597631317786181171d =pi/3v1 =0.0v2 =0.0v3 =0.00000000000000011483642827992216762806615818554(3)a = pi*3^(1/3)b = sym(pi*3^(1/3))c = sym(pi*3^(1/3),'d')d = sym('pi*3^(1/3)')v1=vpa(abs(a-d))v2=vpa(abs(b-d))v3=vpa(abs(c-d))a =4.5310b =1275352044764433/281474976710656c =4.5309606547207899041040946030989d =pi*3^(1/3)v1 =0.00000000000000026601114166290944374842393221638 v2 =0.00000000000000026601114166290944374842393221638 v3 =0.0000000000000002660111416629094726767991785515第二大题:(1)c1=3/7+0.1c1 =0.5286双精度(2)c2=sym(3/7+0.1)c2 =37/70符号(3)c3=vpa(sym(3/7+0.1))c3 =0.52857142857142857142857142857143完整显示精度第三大题:(1)findsym(sym('sin(w*t)'),1)ans =w(2)findsym(sym('a*exp(-X)' ) ,1)ans =a(3)findsym(sym('z*exp(j*theta)'),1)ans =z第四大题:A=sym('[a11 a12 a13;a21 a22 a23;a31 a32 a33]')A =[ a11, a12, a13][ a21, a22, a23][ a31, a32, a33]DA=det(A)DA =a11*a22*a33 - a11*a23*a32 - a12*a21*a33 + a12*a23*a31 + a13*a21*a32 - a13*a22*a31w=inv(A)w =[ (a22*a33 - a23*a32)/(a11*a22*a33 - a11*a23*a32 - a12*a21*a33 +a12*a23*a31 + a13*a21*a32 - a13*a22*a31), -(a12*a33 -a13*a32)/(a11*a22*a33 - a11*a23*a32 - a12*a21*a33 + a12*a23*a31 +a13*a21*a32 - a13*a22*a31), (a12*a23 - a13*a22)/(a11*a22*a33 -a11*a23*a32 - a12*a21*a33 + a12*a23*a31 + a13*a21*a32 - a13*a22*a31)] [ -(a21*a33 - a23*a31)/(a11*a22*a33 - a11*a23*a32 - a12*a21*a33 +a12*a23*a31 + a13*a21*a32 - a13*a22*a31), (a11*a33 -a13*a31)/(a11*a22*a33 - a11*a23*a32 - a12*a21*a33 + a12*a23*a31 +a13*a21*a32 - a13*a22*a31), -(a11*a23 - a13*a21)/(a11*a22*a33 -a11*a23*a32 - a12*a21*a33 + a12*a23*a31 + a13*a21*a32 - a13*a22*a31)] [ (a21*a32 - a22*a31)/(a11*a22*a33 - a11*a23*a32 - a12*a21*a33 +a12*a23*a31 + a13*a21*a32 - a13*a22*a31), -(a11*a32 -a12*a31)/(a11*a22*a33 - a11*a23*a32 - a12*a21*a33 + a12*a23*a31 +a13*a21*a32 - a13*a22*a31), (a11*a22 - a12*a21)/(a11*a22*a33 -a11*a23*a32 - a12*a21*a33 + a12*a23*a31 + a13*a21*a32 - a13*a22*a31)] IAs=subexpr(w,'d')d =1/(a11*a22*a33 - a11*a23*a32 - a12*a21*a33 + a12*a23*a31 + a13*a21*a32 - a13*a22*a31)IAs =[ d*(a22*a33 - a23*a32), -d*(a12*a33 - a13*a32), d*(a12*a23 -a13*a22)][ -d*(a21*a33 - a23*a31), d*(a11*a33 - a13*a31), -d*(a11*a23 -a13*a21)][ d*(a21*a32 - a22*a31), -d*(a11*a32 - a12*a31), d*(a11*a22 -a12*a21)]第六大题:syms ksyms x positives_s=2/(2*k+1)*((x-1)/(x+1))^(2*k+1)s_ss=simple(symsum(s_s,k,0,inf))s_s =(2*((x - 1)/(x + 1))^(2*k + 1))/(2*k + 1)警告: simple will be removed in a future release. Use simplify instead. [> In sym.simple at 41]s_ss =log(x)第八大题:syms x clearsyms xh=exp(-abs(x))*abs(sin(x))si=vpa(int(h,-5*pi,1.7*pi),64)h =abs(sin(x))*exp(-abs(x))si =1.087849417255503701102633764498941389696991336803454392428439159 第九大题:syms x y clearsyms x yr=int(int(x^2+y^2,y,1,x^2),x,1,2)r =1006/105第十大题:syms t x;f=sin(t)/t;y=int(f,t,0,x)y1=subs(y,x,sym('4.5'))ezplot(y,[0,2*pi])y =sinint(x)y1 =syms x clearsyms x ny=sin(x)^nyn=int(y,0,1/2*pi)y31=vpa(subs(yn,n,sym('1/3')))y32=vpa(subs(yn,n,1/3))y =sin(x)^nyn =piecewise([-1 < real(n), beta(1/2, n/2 + 1/2)/2], [real(n) <= -1, int(x^n/(1 - x^2)^(1/2), x, 0, 1)])y31 =1.2935547796148952674767575125656y32 =1.2935547796148952674767575125656第二十题:clearsyms y xy=dsolve('(Dy*y)/5+x/4=0','x')y =2^(1/2)*(C6 - (5*x^2)/8)^(1/2)-2^(1/2)*(C6 - (5*x^2)/8)^(1/2)y1=subs(y,'C6',1)y1 =2^(1/2)*(1 - (5*x^2)/8)^(1/2)-2^(1/2)*(1 - (5*x^2)/8)^(1/2)clfhy1=ezplot(y1(1),[-2,2,-2,2],1)set(hy1,'Color','r')grid onhold onhy2=ezplot(y1(2),[-2,2,-2,2],1)set(hy2,'Color','b')grid onxlabel('Y')ylabel('X')hold offbox onlegend('y(1)','y(2)','Location','Best')hy1 =174.0155hy2 =177.0145。
1,在一个MA TLAB命令中,6+7i和6+7*i有何区别?i和I有何区别?
第一个i代表一个变量,6+7i是一个函数,第二个代表虚数,6是实部,7代表虚步.I只代表变量.
2,.设A和B是两个同大小的矩阵,试分析A*B和A.*B、A./B和B.\A、A/B和B/A的区别?如果A和B是两个标量数据,结论又如何?
A *B是矩阵相乘,A.*B表示A和B单个元素之间对应相乘。
A./B和
B.\A值相等,是一样的。
A/B等效于B的逆右乘A的矩阵,B\A等效于B矩阵逆左乘A矩阵。
如果A和B是两个标量数据,结论是都没有区别。
3,写出完成下列操作的命令。
(1)删除矩阵A的第7号元素
A(7)=[]
(2)将向量t的0元素用机器零来代替
t(find(t==0))=eps
(3)将含有12个元素的向量x转换成3*4矩阵
newA=reshape(A,3,4)
(4) 求一个字符串的ASCII
ch=['a b c';'1 2 3'];
abs ch
(5) 产生和A同样大小的幺矩阵
ones(size(A))
(6) 从矩阵A提取主对角线元素,并以这些元素构成对角阵B。
A=[1 2 3;4 5 6;7 8 9];
D=diag(A)
B=diag([1,5,9])
4, .要生产均值为3,方差为1的500个正态分布的随机序列,写出相应的表达式y=3+sqrt(1)*randn(500)
5,(1)主对角元素1 1 5 9
上三角矩阵1 -1 2 3
0 1 -4 2
0 0 5 2
0 0 0 9
下三角矩阵1 0 0 0
5 1 0 0
3 0 5 0
11 15 0 9
逆矩阵-0.1758 0.1641 0.2016 -0.0227
-0.1055 -0.1016 -0.0391 0.0664
-0.0508 -0.0859 0.1516 0.0023
0.3906 -0.0313 -0.1813 0.0281
行列式的值1280
秩4
范数A1=norm(A,1)=20 A2=norm(A)= 21.3005 A3=norm(A,inf)=35
条件数A1=cond(A,1)= 14.4531 A2=cond(A,2)= 11.1739 A3=cond(A,inf)= 22.0938
迹16
(2)主对角元素0.43 4
上三角矩阵0.4300 43.0000 2.0000
0 4.0000 21.0000
下三角矩阵0.4300 0 0
-8.9000 4.0000 0
逆矩阵0.0022 -0.0175
0.0234 -0.0017
-0.0035 0.0405
行列式的值
秩2
范数B1=norm(B,1)= 47 B2=norm(B)= 43.4271 B3=norm(B,inf)= 45.4300 条件数B2=cond(B,2)= 1.9354
迹4.4300
6,all(A)=0
any(A)=1
isnan(A)= 0 1 0 0 0 0 0
isinf(A)= 0 0 1 1 0 0 0
isfinite(A)= 1 0 0 0 1 1 1。