Question

matlab 为什么算不出结果

y=[-12.761
-12.46
-12.167
-11.904
-11.751
-11.412
-11.137
-10.935
-10.689
-10.388
-10.146
-9.849
-9.592
-9.347
-9.18
-9.01
-8.828
-8.717
-8.671
-8.643
-8.633
];%导入曲线1中的x变量
syms s t p A f;
t=p1*s^9 + p2*s^8 + p3*s^7 + p4*s^6 + p5*s^5 + p6*s^4 + p7*s^3 + p8*s^2 + p9*s + p10
p1 =-0.008927;
p2 =-0.872 ;
p3 =-37.78;
p4 =-952.8 ;
p5 =-1.542e+004 ;
p6 = -1.66e+005;
p7 =-1.189e+006;
p8 =-5.463e+006 ;
p9 =-1.461e+007;
p10 =-1.734e+007 ;%MATLAB求解出的曲线1解析式
p=diff(t);
q=size(y);
f=(s*sqrt(1+p^2));
A=2*pi*simple(int(f,simple(s),y(1),y(q(1))));
disp(A);

Answer 1

改成这样就行了 y=[-12.761
-12.46
-12.167
-11.904
-11.751
-11.412
-11.137
-10.935
-10.689
-10.388
-10.146
-9.849
-9.592
-9.347
-9.18
-9.01
-8.828
-8.717
-8.671
-8.643
-8.633
];%导入曲线1中的x变量
syms s t p A f; p1 =-0.008927;
p2 =-0.872 ;
p3 =-37.78;
p4 =-952.8 ;
p5 =-1.542e+004 ;
p6 = -1.66e+005;
p7 =-1.189e+006;
p8 =-5.463e+006 ;
p9 =-1.461e+007;
p10 =-1.734e+007 ;%MATLAB求解出的曲线1解析式
t=p1.*s.^9 + p2.*s.^8 + p3.*s.^7 + p4.*s.^6 + p5.*s.^5 + p6.*s.^4 + p7.*s.^3 + p8.*s.^2 + p9.*s + p10

p=diff(t);
q=size(y);
f=(s*sqrt(1+p^2));
A=2*pi*simple(int(f,simple(s),y(1),y(q(1))));
disp(A);
要用“.*或.^”,还要交换p1，p2,..,p10和t的顺序。运行结果如下：
t =

-5146065135812661/576460752303423488*s^9-109/125*s^8-1889/50*s^7-4764/5*s^6-15420*s^5-166000*s^4-1189000*s^3-5463000*s^2-14610000*s-17340000

Warning: Explicit integral could not be found.
> In sym.int at 58
2*pi*int(1/72057594037927936000*s*(1108306668277667072744712890341949383897929220096000000+6668237767311965765960500214379546624917504000000*s^9+80884381386033773393003733503392145140088832000000*s^8+774458439024146521971353462653952895630704640000000*s^7+5833952777329518648152090889652260968385740800000000*s^6+34211057962943356046481471857856308330889216000000000*s^5+153100475362209751706232868672593759043584000000000000*s^4+1657680856618991609277653208535177227141120000000000000*s+505460566121333199693917835658315897503744000000000000*s^3+1161024660588801575400329394282466677620736000000000000*s^2+33516264014752391708495623749603140625*s^16+5820281985161437990810833984386236416000*s^15+473327681651493400322803235874685421879296*s^14+23927950537506279516871635395629510106808320*s^13+841613041390095986005234064133410090332979200*s^12+21839447339494184052337219698216361185509376000*s^11+432512249185173762321398224809598812988375040000*s^10)^(1/2),s = -12761/1000 .. -8633/1000)

追问

我按你说的写了，并把最后一句改成了double(A),但提示
Warning: Explicit integral could not be found.
> In sym.int at 58
并且A
=2*pi*int(1/72057594037927936000*s*(110830666827766707274471289034194900)………………

怎么才能让算出来的值正常显示呢？

追答

s的值是未知的，无法计算出具体数值

追问

int(f,simple(s),y(1),y(q(1)))中确定了上下限啊

追答

出现警告好像是int后的f要用单引号吧。式子有点复杂，看得眼都花了