I tried all day to run my code syms R t; eqn = R*tan(1002​2.99039*R)​-(6.97964*​10^-3*sqrt​(t))/R==0 ; m = linspace(10,20,1) ; sol = zeros(size(t)) ; for i =1 :length(m) eqn = subs(eqn,t,m(i)) ; sol(i) = double(solve(eqn,R)) ; end plot(m,sol)

this is my code

syms R t;
eqn = R*tan(10022.99039*R)-(6.97964*10^-3*sqrt(t))/R==0 ;

m = linspace(10,20,1) ;
sol = zeros(size(t)) ;
for i =1 :length(m)
    eqn = subs(eqn,t,m(i)) ;
    sol(i) = double(solve(eqn,R)) ;
end
plot(m,sol)

But when I running matlab give me the following issues

Error using mupadmex
Internal error with symbolic engine. Quit and restart MATLAB.

Error in sym>cell2ref (line 1303)
S = mupadmex(y);

Error in sym>tomupad (line 1241)
    S = cell2ref(numeric2cellstr(x));

Error in sym (line 215)
                S.s = tomupad(x);

Error in syms (line 197)
toDefine = sym(zeros(1, 0));

Error in SOLUCION1 (line 3)
syms R t;

any suggetion?

Answer 1

[Ameer Hamza]

It seems that there is some problem with symbolic math toolbox. If you are using R2017b or R2018a on windows 10 then you might try this recent update: https://www.mathworks.com/support/bugreports/1755918.

[alburary daniel]

it works but now I have this Warning: Unable to solve symbolically. Returning a numeric approximation instead. > In solve (line 304) In SOLUCION1 (line 10) >> SOLUCION1 Warning: Unable to solve symbolically. Returning a numeric approximation instead. > In solve (line 304) In SOLUCION1 (line 10) >> some idea?

[Ameer Hamza]

You are getting this warning because the analytical solution of this equation does not exist. In this non-linear equation, you cannot write a closed form solution of the form

R = f(t)

where f is an analytical function. Therefore, MATLAB gives this warning and return a numeric solution instead.

[Walter Roberson]

There are an infinite number of solutions. The normal value of the function is about -1E47, so you only get a zero of the function when tan(10022.99039*R) approaches infinity close enough to overcome the -1E47. The function is highly non-linear there, so finding the correct value is difficult.