From mboxrd@z Thu Jan  1 00:00:00 1970
From: Miguel Ruiz <rbenit68@openmailbox.org>
Subject: Re: Two numerical solutions from fsolve inside calc source block
Date: Sat, 02 Jul 2016 13:30:05 +0200
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Better yet:

#+begin_src calc :wrap "src calc :var var-s2=3D1"
fsolve([8.66e10 =3D r * v, -7.51e6 =3D 0.5*v^2 - 6.67e-11*6e24/r],[r,v])
#+end_src



El 2016-06-26 15:53, Miguel Ruiz escribi=C3=B3:
> Hi,
>=20
> I have this block which is intended to get the two numerical solutions
> of the equations system:
>=20
> #+begin_src calc
> fsolve([8.66e10 =3D r * v, -7.51e6 =3D 0.5*v^2 - 6.67e-11*6e24/r],[r,v]=
)
> #+end_src
>=20
> This way I get the generic form of a multiple solution, and citing the
> manual "It will invent variables n1, n2, =E2=80=A6, which represent
> independent arbitrary integers, and s1, s2, =E2=80=A6, which represent
> independent arbitrary signs (either +1 or -1)."
>=20
> So I get
>=20
> #+RESULTS:
> : [r =3D 86600000000. / (4621.24711316 - 2517.12631405 s1), v =3D
> 4621.24711316 - 2517.12631405 s1]
>=20
> Now, to get the two solutions I have to evaluate manually the result
> expression replacing s1 by "*1" and "*-1"
>=20
> #+begin_src calc
> [r =3D 86600000000. / (4621.24711316 - 2517.12631405 *1), v =3D
> 4621.24711316 - 2517.12631405 *1]
> #+end_src
>=20
> #+RESULTS:
> : [r =3D 41157332.8093, v =3D 2104.12079911]
>=20
> And
>=20
> #+begin_src calc
> [r =3D 86600000000. / (4621.24711316 - 2517.12631405 *-1), v =3D
> 4621.24711316 - 2517.12631405 *-1]
> #+end_src
>=20
> #+RESULTS:
> : [r =3D 12131615.2598, v =3D 7138.37342721]
>=20
> Emacs calc manual states "Note that variables like n1 and s1 are not
> given any special interpretation in Calc except by the equation solver
> itself. As usual, you can use the s l (calc-let) command to obtain
> solutions for various actual values of these variables.", but I cannot
> figure out a way to call (calc-let) or its algebraic equivalent inside
> a calc source block.
>=20
> I can accept a only-elisp workaround if it is more convenient.
>=20
> Any hint to do everything commented without user interaction?
>=20
> Regards.