Defect: (%i6) inverse_outative(1 / (2* f(x)),f); (%o6) 1/(2*f(x)) The internal representation of 1 / (2* f(x)) is effectively (1/2) * (f(x))^-1, not 1/(2 * f(x)). Fixing this particular case wouldn't be all that difficult. --Barton -