Example 1: 
 
   > autosimplify = on !;
 
   > print(x - x);
 
   0
 
   > autosimplify = off ;
 
   Automatic pure tree simplification has been deactivated.
 
   > print(x - x);
 
   x - x
 
 
 
Example 2: 
 
   > autosimplify = on !; 
 
   > print(rationalapprox(sin(pi/5.9),7));
 
   0.5
 
   > autosimplify = off !; 
 
   > print(rationalapprox(sin(pi/5.9),7));
 
   1 / 2