On Wed, Nov 10, 2004 at 10:06:42AM -0600, Barton Willis wrote:
> Illustration of what I mean by "work too hard to try to apply the
> even / odd function simplifications"
>
> (%i1) assume(x<0);
> (%o1) [x < 0]
> (%i2) sin(x);
> (%o2) - SIN(- x)
>
> It seems gratuitous to apply the odd function rule in this case. We need
> a reasonable heuristic for deciding when to apply the even / odd
...
The above transformation seems metodologically wrong.
In a symbolic system, the '-' sign presence should trigger simplification,
but not the argument's positivity/negativity. Thus, after the odd function rule
application, we should have:
sin(-x) goes to -sin(x) independently of what is known about the x sign,
and, of course,
sin(x) goes to sin(x), again independently of what is known about the x sign.
Best wishes,
--
Alexander