Re: broadcasting of Equal ? (newbie question)
- To: mathgroup at smc.vnet.net
- Subject: [mg118164] Re: broadcasting of Equal ? (newbie question)
- From: Murray Eisenberg <murray at math.umass.edu>
- Date: Fri, 15 Apr 2011 03:55:05 -0400 (EDT)
This indeed seems to be an oversight in the reference page for Solve.
Perhaps due to the fact that Threading Equal over lists -- which,
technically, is what Solve is doing -- came relatively late to
Mathematica (version 5?).
Definitely something worth reporting to Wolfram Research as a suggestion.
There actually is something about this in the documentation, but in a
different place: tutorial/SimultaneousEquations. About 2/3 or 3/4 down
the page there you'll find a box with caption "Ways to present
simultaneous equations to Solve". The third of the three ways listed
there is with a list on the left of == and a corresponding list on the
right. And just one example:
{{3, 1}, {2, -5}}.{x, y} == {7, 8}
Solve[%, {x, y}]
To my mind, that example is not optimal in that it ought to be put
directly, or eventually, in the form:
Solve[ {{3, 1}, {2, -5}}.{x, y} == {7, 8}, {x, y}]
Or perhaps even more directly in the form:
Solve[{3x + y, x - 5y} == {7, 8}, {x, y}]
And, in any case, mention and example of such implicit Threading should
go on the reference page for Solve, too.
On 4/14/2011 4:49 AM, Alan wrote:
> I noticed that e.g.
> Solve[{x + y - 1, 2 x + y - 2} == {0, 0}, {x, y}]
> can be written as
> Solve[{x + y - 1, 2 x + y - 2} == 0, {x, y}]
> but I cannot find the rule that allows this.
> (E.g., I do not find it in the help for Equal
> or the help for Solve.)
>
> Can you point me to it?
>
> Thanks,
> Alan
>
--
Murray Eisenberg murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower phone 413 549-1020 (H)
University of Massachusetts 413 545-2859 (W)
710 North Pleasant Street fax 413 545-1801
Amherst, MA 01003-9305