isolate a variable?

I can isolate one variable as an expression? example:

'x^2+2+x' em 'x = x^2 +2'

 remembering that they are symbolic objects.

 Thanks in advance.

Answer 1

[Walter Roberson]

If your input is x^2 + 2 + x then you cannot isolate x to one side of an equation, as your input is not an equation.

If your input is implicitly x^2 + 2 + x = 0 then your example output of x = x^2 + 2 is incorrect: instead x = -x^2 - 2

You cannot always isolate one variable -- not unless you are willing to make some restrictions on the form of the equation.

If you have a polynomial as input, then

S = x^2+2+x;
c = sym2poly(S);
isolated_x = x * c(end-1) - S;

[Artur M. G. Lourenço]

Thank you and sorry for having written the equation the wrong way. However I could not do the same for this equation:

f = x * pi * sqrt (x ^ 2 +20 ^ 2);

it is possible to do in the Symbolic Math Toolbox?

[Walter Roberson]

Usually what you do is solve() for a variable, rather than try to isolate the variable.

You could try working with map() and coeff(), but as I do not have the Symbolic Toolbox I am not certain what result you will get for terms that do not have the variable. The coeff() page indicates that FAIL should be returned; I do not know what FAIL translates to when moved from the MuPad side to the MATLAB side.