MathAction #273 Factor Expression Integer does nothing

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axiom factor ((y-1) * x + y - 1)

is right

$\label{eq1}{\left(x + 1 \right)}\ {\left(y - 1 \right)}$

Type: Factored(Polynomial(Integer))

axiom

factor ((y-1) * sin x + y - 1) -- does nothing

$\label{eq2}{{\left(y - 1 \right)}\ {\sin \left({x}\right)}}+ y - 1$

(2)

Type: Factored(Expression(Integer))

(new) --Martin Rubey, Sat, 04 Mar 2006 12:56:00 -0600 reply

This is "obvious" since EXPR is a field...

Martin

status change --greg, Sun, 02 Apr 2006 13:09:15 -0500 reply

I think we can close this issue. Are you agree ?

well documented and more or less mathematically sound --kratt6, Mon, 03 Apr 2006 05:01:02 -0500 reply

Status: open => closed

For others who may find this --daniel, Mon, 08 Jan 2007 20:21:34 -0600 reply

While this is "mathematically sound", it can be very frustrating to new users of Axiom. Is this behavior explained in a FAQ somewhere? Maybe something should be added to section 8.2 of the 30-year book?

To get what the OP wanted, recast the problem as a Polynomial:
f:=(y-1)*sin(x)+y-1 -- original function
g:=subst(f, sin(x)=sx)::Polynomial Integer -- remove the nonlinear operators, then recast
h:=factor(g) -- yields (sx + 1)(y - 1)

Unfortunately, any conversion of h from a "Factored Polynomial Integer" to a "Factored Expression Integer" will destroy the factorization.

... --kratt6, Fri, 28 Dec 2007 14:56:30 -0800 reply

Category: Axiom Mathematics => Axiom Library

Subject: (replying) Be Bold !!

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