rtoy
commented
3 months ago Imported from SourceForge on 2024-07-04 14:59:36 Created by willisbl on 2007-03-24 11:06:16 Original: https://sourceforge.net/p/maxima/bugs/1152/#e5ba
Logged In: YES user_id=895922 Originator: NO
A related bug is 939022.
Imported from SourceForge on 2024-07-04 14:59:35 Created by macrakis on 2007-03-21 16:48:39 Original: https://sourceforge.net/p/maxima/bugs/1152
matrix([ 1, taylor(x,x,0,1)], [taylor(y,y,0,1), 1 ]) ^^ -1 => matrix([ -1/(y^2-1) , y/(y^2-1) ], [ y/(y^2-1) , -1/(y^2-1) ])
which is very wrong (it has apparently conflated variables x and y -- depending on the previous session history, it may return a result in x or in y). This happens both with ratmx=false and ratmx=true.
To calculate the correct answer:
subst([a=taylor(x,x,0,1),b=taylor(y,y,0,1)], matrix([1,a],[b,1])^^-1 ) => matrix([1+x*y+...,-x+...],[-y+...,1+x*y+...])
Not sure whether this is a problem in the matrix code or the taylor code.