# calculating residue with maxima_methods

 1 The following used to work around six months ago on sagenb.org: var('x') var('t') ( x/((4*x - 1)*(t^2 - t + x)) ).maxima_methods().residue(t,(1-sqrt(1-4*x))/2)  but now it returns zero which is incorrect. Can anybody help me get the correct answer again? asked Jul 07 '12 Stefán Ingi 13 ● 3

 2 sage: from sympy import Symbol, residue sage: x = Symbol("x") sage: t = Symbol("t") sage: residue(x/((4*x - 1)*(t^2 - t + x)),t,(1-sqrt(1-4*x))/2) -x/((-4*x + 1)**(1/2)*(4*x - 1))  posted Jul 07 '12 achrzesz 1741 ● 5 ● 18 ● 39 I didn't know Sympy had this... see also http://trac.sagemath.org/sage_trac/ticket/11210kcrisman (Jul 07 '12)
 0 I get this in a very old version of Sage's Maxima, the current Sage Maxima, and the most recent one I have. Maxima 5.27.0 http://maxima.sourceforge.net using Lisp SBCL 1.0.24 Distributed under the GNU Public License. See the file COPYING. Dedicated to the memory of William Schelter. The function bug_report() provides bug reporting information. (%i1) residue(( x/((4*x - 1)*(t^2 - t + x)) ),t,(1-sqrt(1-4*x))/2); (%o1) 0  What/when was the answer you got before? I can't get this to do anything else in any version of Sage, either, not just the Maxima in it. This is now Maxima artifact 3541292; I've also put it at the relevant Sage ticket. posted Jul 07 '12 kcrisman 7802 ● 20 ● 78 ● 170 I was reexamining my old code and found the culprit. When it worked before I had run "assume(x<1/8)". That makes maxima give the same answer as sympy. Sorry for the trouble, but at least I learned something about sympy.Stefán Ingi (Jul 24 '12)Hmm, that's interesting. I'll add that to the bug report.kcrisman (Jul 24 '12)