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Re: Help with Solve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg112339] Re: Help with Solve
  • From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
  • Date: Fri, 10 Sep 2010 04:47:45 -0400 (EDT)
  • References: <i6a5i6$kne$1@smc.vnet.net>

Use Reduce instead of Solve. In the words of the documentation
(tutorial/SolvingEquations):

"Solve is set up to give you generic solutions to equations. It
discards any solutions that exist only when special constraints
between parameters are satisfied.

If you use Reduce instead of Solve, Mathematica will however keep all
the possible solutions to a set of equations, including those that
require special conditions on parameters."

Cheers -- Sjoerd


On Sep 9, 10:23 am, Eduardo  Cavazos <wayo.cava... at gmail.com> wrote:
> Hello!
>
> A newb question I'm sure... :-)
>
> Here's a couple of equations:
>
> eq1 = n*Sin[x] == (m*v^2)/r;
> eq2 = n*Cos[x] == m*g;
>
> The goal is to solve for 'x'.
>
> I can do this in a roundabout way via:
>
>     Solve[eq1 /. Solve[eq2, n], x]
>
> I.e. solve eq2 for 'n', substitute this into eq1, and solve the result
> for 'x'. But this approach seems too "manual".
>
> Is there a more straightforward way to carry out the problem? I tried
> this:
>
>     Solve[{eq1, eq2}, x]
>
> but it doesn't seem to work. What's a good way to go about this?
>
> Thanks!
>
> Ed



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