2011-12-23 20:10:25 +0100 received badge ● Supporter (source) 2011-12-23 20:09:36 +0100 answered a question Taylor expansion twice for a general function cause problem? Hello, I'm new to Sage and running into the same problem as you. I think this error happens when the object that you want to Taylor expand has a derivative that is evaluated at a specified point: x = var('x') u = function('u', x) v(x) = u.diff(x) taylor(u(x = 0), x, 0, 2) #works taylor(v(x), x, 0, 2) #works taylor(v(x = 0), x, 0, 2) #doesn't work  v(0) = D[0](u)(0) seems to be the problem, just like, in your case, there is a D[0](f)(0) in the Taylor expansion of g So my guess is that issue resides in how derivatives evaluated at a fixed point are passed to Maxima..