Re: Two numerical solutions from fsolve inside calc source block

[Miguel Ruiz <rbenit68@openmailbox.org>]

Better yet:

#+begin_src calc :wrap "src calc :var var-s2=1"
fsolve([8.66e10 = r * v, -7.51e6 = 0.5*v^2 - 6.67e-11*6e24/r],[r,v])
#+end_src



El 2016-06-26 15:53, Miguel Ruiz escribió:
> Hi,
> 
> I have this block which is intended to get the two numerical solutions
> of the equations system:
> 
> #+begin_src calc
> fsolve([8.66e10 = r * v, -7.51e6 = 0.5*v^2 - 6.67e-11*6e24/r],[r,v])
> #+end_src
> 
> This way I get the generic form of a multiple solution, and citing the
> manual "It will invent variables n1, n2, …, which represent
> independent arbitrary integers, and s1, s2, …, which represent
> independent arbitrary signs (either +1 or -1)."
> 
> So I get
> 
> #+RESULTS:
> : [r = 86600000000. / (4621.24711316 - 2517.12631405 s1), v =
> 4621.24711316 - 2517.12631405 s1]
> 
> Now, to get the two solutions I have to evaluate manually the result
> expression replacing s1 by "*1" and "*-1"
> 
> #+begin_src calc
> [r = 86600000000. / (4621.24711316 - 2517.12631405 *1), v =
> 4621.24711316 - 2517.12631405 *1]
> #+end_src
> 
> #+RESULTS:
> : [r = 41157332.8093, v = 2104.12079911]
> 
> And
> 
> #+begin_src calc
> [r = 86600000000. / (4621.24711316 - 2517.12631405 *-1), v =
> 4621.24711316 - 2517.12631405 *-1]
> #+end_src
> 
> #+RESULTS:
> : [r = 12131615.2598, v = 7138.37342721]
> 
> 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.
> 
> I can accept a only-elisp workaround if it is more convenient.
> 
> Any hint to do everything commented without user interaction?
> 
> Regards.