If you insist, you can force all three to deliver a floating point answer. In Maxima you'd do it as follows:

(C39) ev(%,numer); (D39) 0.5333783737377914 (C40)whereas in Maple the corresponding command is:

> evalf(%); .5333783739 >

In Mathematica function `N` evaluates an algebraic expression
with accuracy requested by its second argument:

In[16]:= N[%,10] Out[16]= 0.5333783737 In[17]:=