Re: [Maxima-discuss] Why does 'solve' not work here?

[Mark <zei...@ya...>]

On 02/15/2014 05:28 PM, Richard Fateman wrote:
>> Given the two simultaneous equations:
>> sin(y) = 0
>> sin(x-y) = sin(y)
>> will Maxima solve them using a single input command, calling just a
>> single one of its built in functions?
> So far as I can tell, there is no single current built-in function
> that will solve this problem.

Ok. Simple question. Simple answer. Thanks.

The rest of you answer seems not completely Maxima related, but was kind
of fun too.

> Let me ask you an analogous question.  Can you make a sandwich with a
> single piece of
> bread using your standard method of making a sandwich with two pieces
> of bread?
>
> (My) answer:  No.   But I can make a sandwich by folding a single
> piece of bread or cutting it in half, etc.

(My) answer: Yes.  With so many competing bakeries around, why starve
from less lunch? Go and get yourself the second piece of bread everyone
else is enjoying already.

>> If so, which built in function?
> Why must all tasks be solved by a single built-in function?  Why not a
> combination?

That's a simple one: because when humble-me turns to a CAS I expect the
CAS to tell me the solution - not vice versa.

>   For example, if
> you took the inputs, converted them to exponentials you could make
> some headway. e.g.
> to_poly_solve(exponentialize([(sin(x-y)-sin(y)=0),sin(y)=0],[exp(-%i*x),exp(-%i*y)]);
>

That's the same point I already made in my question: there are many ways
to solve such kind of equations with several in-between-steps. Your's is
one. The one I gave is another one. As you know, I could 'map' the
asin() function to the list of equations and then call 'solve' which can
also be written in one line.

>> But that's not what I'm looking for.
> No, apparently what you want is to have a somewhat longer and in some
> cases slower
>  program that spends some  more time looking for trivial solutions.

No. Totally misunderstood.
What I want from a CAS is a 'solve' command that I can rely on to do the
simple things right, before I apply it to a case where neither I nor you
can just guess the solution.

Actually there is an analogous question I have to you:
There is a grad student wanting to joint a project of your's. So you
tell the student that you have one piece of bread and that you take
another piece of bread and that you place it on top of the first one.
Now you ask the student: how many pieces of bread do I have on the
stack? The student answers: I cannot solve this.
Would you rely on this student to do part of your actual research?

(My) answer: No.  (and actually I would not rely on halfing the student
either ;) )


-M