#473 Factor doesn't look inside fractional power

open
nobody
Lisp Core (472)
5
2006-07-19
2003-12-17
Stavros Macrakis
No

factor(sqrt(x^2-1)) => doesn't factor
should be sqrt(x-1)*sqrt(x+1)

factor((t^2+2*t+1)^(1/3)) => doesn't factor
should be (t+1)^(2/3)

and perhaps the most surprising:

factor(sqrt(t^2+2*t+1)) => doesn't factor
should be (t+1) or abs(t+1)

Workaround is to use scanmap(factor,expr).

I am not suggesting that factor should factor all
subexpressions (like scanmap). In these cases, it is a
top-level factorization that is being missed.

Discussion

  • Robert Dodier
    Robert Dodier
    2006-07-19

    • labels: --> Lisp Core
     
  • Robert Dodier
    Robert Dodier
    2006-07-19

    Logged In: YES
    user_id=501686

    Observed in 5.9.3cvs.