If you want to save typing, try
s(x):=ratsubst(1,u^2+v^2+w^2,x);
then type
s(%);
every so often.
or you could define a rule and use
tellsimp or tellsimpafter.
Then it would be used automatically,
but perhaps too much.
As for ::
it is almost never used. It certainly
doesn't do what you seem to think it does.
Why not just set w: sqrt(1-u^2-v^2).
RJf
BadDogSprocket wrote:
> All:
>
> I have an expression involving a vector p = [u, v, w]'
> for which it is known in advance that |p| == 1, i.e.
> the point p lies on the unit sphere. I am doing some
> manipulations that result in equations involving the
> expression u^2 + v^2 + w^2, and it would be nice if
> Maxima would automatically replace this expression
> with unity without me having to type
>
> ratsubst(1, u^2 + v^2 + w^2, %);
>
> after every other command. I'm getting Carpal Tunnel
> over here.
>
> Is there a way to do this? I tried using the "::"
> operator, which from the documentation, seems like it
> should accomplish what I want, but:
>
> 1 :: u^2 + v^2 + w^2;
>
> yields an "invalid assignment" error.
>
> Related uestion: if this is not what "::" is
> supposed to do, then what *does* it do, exactly?
>
> Robert: I suggest you answer the question 'What is
> the difference between ":" and "::"' with examples in
> your minimal-maxima guide.
>
> Dan
>
> P.S. Has anyone ever been able to successfully post a
> new topic to this group through the gmane.org web
> interface? Every time I try, the web interface seems
> to accept my post, but withing five minutes, the mail
> server bounces my post back at me.
>
>
>
>
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