Question

I don’t have the slightest idea what’s going on here, and Google provides no interesting help. I took the following example from http://www.mathworks.com/help/toolbox/symbolic/solve.html#inputarg_eqn

>> syms x
>> solve(x^2 + 4*x + 1 == 0)
??? Error using ==> char
Conversion to char from logical is not possible.

Error in ==> solve>getEqns at 169
   vc = char(v);

Error in ==> solve at 67
[eqns,vars] = getEqns(varargin{:});

What’s going on here?

Answer 1

The documentation you’re reading doesn’t apply to your version of MatLab. I can reproduce your error in 2008b, for example.

The older documentation says:

Note that these examples assume equations of the form f(x) = 0. If you need to solve equations of the form f(x) = q(x), you must use quoted strings. In particular, the command

s = solve('cos(2*x)+sin(x)=1')

In the future, pay attention to the line at the top of every MatLab online documentation page where it says what version the documentation applies to.