Maple cannot determine whether something is true or false in an if statement or while clause.

 A typical occurrence happens when a procedure that requires numeric arguments is called with symbolic arguments:

Solution:

Maple evaluates the inputs to a procedure such as plot before it calls the procedure, resulting in  being called with the symbolic argument . Since  has not yet been assigned a value, Maple cannot determine if  is less than . You can either delay the evaluation of the input using unevaluation quotes, or you can supply the arguments with operator form. For details, see uneval.

  fsolve, Numerical integration,  plot , uneval