2011-01-26 09:14, Minh Nguyen skrev:
On Wed, Jan 26, 2011 at 6:41 PM,<xl...@free.fr> wrote:
sage: sqrt(2)*sqrt(3)-sqrt(6)
sqrt(2)*sqrt(3)-sqrt(6)
I would expect results sqrt(6) and 0...
I try with the command simplify() but it doesn't do anything.
> In the above Sage session, you declared two symbolic expressions. So
> it is possible to use methods defined on symbolic expressions other
> than simplify(). In the present case, you want to use the
> simplify_radical() method to simplify radicals:
Thanks.
However...
I am surprised that simplify is sufficient on symbolic variables
denoting positive numbers:
sage: assume(x>0, y>0)
sage: (sqrt(x)*sqrt(y)-sqrt(x*y)).simplify()
0
sage: (sqrt(2)*sqrt(3)-sqrt(2*3)).simplify()
sqrt(2)*sqrt(3) - sqrt(6)
I am particularly surprised by:
sage: (sqrt(x)*sqrt(y)-sqrt(x*y)).subs(x=2)
0
sage: (sqrt(x)*sqrt(y)-sqrt(x*y)).subs(x=2, y=3).simplify()
sqrt(2)*sqrt(3) - sqrt(6)
(We did not even need the call to simplify when substituting only x=2.)
Is it reasonable to consider the last example a bug?
Of course, the answer sage gives is correct, but it is certainly not the
behaviour I would expect.
Regards
Johan
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