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Section: Function Related Functions
Finds the symbolic variables in an expression. The syntax for its use is
syms = symvar(expr)
 where expr is a string containing an expression, such as 'x^2 + cos(t+alpha)'. The result is a cell array of strings containing the non-function identifiers in the expression. Because they are usually not used as identifiers in expressions, the strings 'pi','inf','nan','eps','i','j' are ignored. 
Here are some simple examples:
--> symvar('x^2+sqrt(x)')  % sqrt is eliminated as a function
ans = 
 [x] 
--> symvar('pi+3')         % No identifiers here
ans = 
  Empty array 0x1
--> symvar('x + t*alpha')  % x, t and alpha
ans = 
 [alpha] 
 [t] 
 [x]