#561 matrix(...taylor...)^^-1 wrong

open
nobody
5
2006-04-09
2004-04-21
Stavros Macrakis
No

Consider

m: matrix([taylor(1+a*x,x,0,1),0],
[0,taylor(1+d*x,x,0,1)]);

Now,

m^^-1
=> matrix([1/(d*x+1),0],[0,1/(d*x+1)])

There are two problems with this. First, the answer is
incorrect. Compare:

matrixmap(ratdisrep,m)^^-1
=> matrix([1/(a*x+1),0],[0,1/(d*x+1)])

Second, the answer is not in terms of taylor series. A
silent ratdisrep was done in the middle, losing truncation
information.

Discussion

  • Robert Dodier
    Robert Dodier
    2006-04-09

    • labels: --> Lisp Core - Taylor