Re: confused about asserting variable is element of
- To: mathgroup at smc.vnet.net
- Subject: [mg103089] Re: [mg103084] confused about asserting variable is element of
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Tue, 8 Sep 2009 05:54:45 -0400 (EDT)
- Reply-to: hanlonr at cox.net
funcs = {Simplify, FullSimplify, Refine};
Use Assuming
Assuming[{Element[a, Reals]},
#[Im[a]]] & /@ funcs
{0,0,0}
Use the Assumptions option
#[Im[a], Assumptions ->
Element[a, Reals]] & /@ funcs
{0,0,0}
Use the Assumptions option short form
#[Im[a], Element[a, Reals]] & /@ funcs
{0,0,0}
Or add your assumption to $Assumptions
$Assumptions = Element[a, Reals];
#[Im[a]] & /@ funcs
{0,0,0}
Bob Hanlon
---- dushan <dushanm at spinn.net> wrote:
=============
I'm still learning Mathematica (using 7.0.1) and don't understand
Mathematica's response. After finally finding out how to assert that a
variable is real, I tried to verify this by asking Mathematica to show me that
it knew the imaginary part of the variable is zero. But I couldn't
find a way to do that.. Here're my instructions:
In[1]:= a (ESC)el(ESC) Reals
Out[1]:= a (the element-of symbol) Reals
In[2]:= ##Im[a]
Out[2]:= Im[a]
where '##' is any of {null, Refine[, Simplify[, FullSimplify[}. I
also tried some other combinations, such as 'a^2 - Re[a]^2', but these
didn't help either.
What am I doing wrong? How do I verify such things?
Thanks.
- Dushan Mitrovich