Solve equation (unrecognized function or variable)

Dear MatLab Comunity,

I have to solve this equation but it keeps saying that the variable 't' is unrecognized. I should have the plugins for the function 'solve' so I don't understand where is the problem.

N = 5.62 
R = 6.40
W = 600 

eqn = (10 + 2.*W.^(2).*t.^(2) - 8.*W.^(4).*t.^(4))./(10 +23.*W.^(2).*t.^(2) + 4.*W.^(4).*t.^(4)) -N./R

S = solve(eqn, t)

Any help would be appreciated!

All the best,

Alex

Answer 1

[Stephan]

% define t as symbolic
syms t
N = 5.62; 
R = 6.40;
W = 600;

eqn = (10 + 2.*W.^(2).*t.^(2) - 8.*W.^(4).*t.^(4))./(10 +23.*W.^(2).*t.^(2) + 4.*W.^(4).*t.^(4)) -N./R

eqn = 

S = solve(eqn, t)

S = 

% scalar solutions, only real
S1 = vpasolve(eqn,t, [-Inf Inf])

S1 = 

[Alessandro Ruda]

Thank! I had to install another plug in but it works, but what if I want a single scalar number?

[Stephan]

Then use:

% define t as symbolic
syms t
N = 5.62; 
R = 6.40;
W = 600;
eqn = (10 + 2.*W.^(2).*t.^(2) - 8.*W.^(4).*t.^(4))./(10 +23.*W.^(2).*t.^(2) + 4.*W.^(4).*t.^(4)) -N./R

eqn = 

% scalar solutions, only real
S1 = vpasolve(eqn,t, [-Inf Inf])

S1 = 

change bounds from -Inf to zero to get only the positive solution:

S2 = vpasolve(eqn,t, [0 Inf])

S2 = 

0.00042280651261763657433032919695881

[Alessandro Ruda]

Thanks Stephan!