How to fix the sym/solve error

Question

Randy Chen 2021-10-26

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1572288-how-to-fix-the-sym-solve-error

回答： Paul 2021-10-26

I get the following error from my code:

z = [-6.41 -12.4 2.143 102];
r = [13.58 15.7636 12.96 46.6];
syms A B C D;
eq1 = A*r(1)^2+B*z(1)+C*r(1)+D ==0;
eq2 = A*r(2)^2+B*z(2)+C*r(2)+D ==0;
eq3 = A*r(3)^2+B*z(3)+C*r(3)+D ==0;
eq4 = A*r(4)^2+B*z(4)+C*r(4)+D ==0;
solve([eq1,eq2,eq3,eq4],[A,B,C,D])
>> solve([eq1,eq2,eq3,eq4],[A,B,C,D])
Error using sym/solve (line 89)
Error using maplemex
Error, (in MTM:-solve) Vector[row](4, [0,0,0,0], datatype = integer[1]) is not valid equation or expression

And when I tried to display the path of the symbolic solve, here is the result:

>> which -all solve
D:\Softwares\toolbox\maple\solve.m
D:\Softwares\toolbox\maple\@sym\solve.m              % sym method
D:\Softwares\toolbox\symbolic\symbolic\@sym\solve.m  % sym method

How should I fix this issue?

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Answer 1

Paul 2021-10-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1572288-how-to-fix-the-sym-solve-error#answer_817228

在 MATLAB Online 中打开

What version are you using? Seems to work ok here, but w/o any references to Maple.

which -all solve
/MATLAB/toolbox/symbolic/symbolic/@sym/solve.m  % sym method
z = [-6.41 -12.4 2.143 102];
r = [13.58 15.7636 12.96 46.6];
syms A B C D;
eq1 = A*r(1)^2+B*z(1)+C*r(1)+D ==0;
eq2 = A*r(2)^2+B*z(2)+C*r(2)+D ==0;
eq3 = A*r(3)^2+B*z(3)+C*r(3)+D ==0;
eq4 = A*r(4)^2+B*z(4)+C*r(4)+D ==0;
sol = solve([eq1,eq2,eq3,eq4],[A,B,C,D])
sol = struct with fields:
    A: 0
    B: 0
    C: 0
    D: 0