CAS view - Keep symbolic result

Luca Moroni shared this question 3 years ago
Answered

I'm rather new to CAS.

I'd like to know if it's possible to keep the symbolic result in a CAS cell even after some parameter is set in the Algebra view.

For instance, I input in the cell $1

  1. SolveODE(y'=-k y)

Correctly the symbolic result is shown as

  1. -> y = c_1 ℯ^{-k x}

If I need to make (say) a plot I must create a slider for the parameters k and c_1 and assign the result to some variable of the Algebra view, but, doing so, I lose the general symbolic result that I'd like to keep in the CAS view (for reference).

Is it possible to "freeze" the CAS cell display to its symbolic (unevaluated) content?

Does it make sense?


Thanks

Comments (4)

photo
1

Try this, where a & b are numbers in the Algebra View


  1. Substitute($1, {c_1=a,k=b})

photo
1

Thanks Michael. I've seen the Substitute command.

The problem is that I'd like not have duplicated parameter names in the Algebra and Cas views since I'm working on a file with many parameters named with their usual conventional letters used in physics.

Another workaround could be to input, in the CAS view

  1. SolveODE(y'=-"k" y)

with each parameter not to be evaluated "textified", and input in another cell the "untextified" formula for its use in the Algebra view.

I wondered if there was a more convenient solution.

photo
1

perhaps?

photo
1

Thanks mathmagic: that's another excellent workaround.

Actually the Ode i'm working on is

  1. SolveODE(v''=-v (q B/m)^2+(q/m)^2 E B, v, t, (0, v0x), (0, (q B v0y)/m))

with parameters B, E, q, m v0x, v0y and independent variable t.

So making a multivariable function with all those parameters would be rather awkward.

I was rather thinking about a command like

  1. Symbolic[SolveODE(v''=-v (q B/m)^2+(q/m)^2 E B, v, t, (0, v0x), (0, (q B v0y)/m)), {q,B}]

that would keep the parameters in the list at the end {q,B} unevaluated and evaluate all the rest.

I understand that such a command (or a similar one) doesn't exist and maybe it's not so much important as to request its implementation.

So, in my case, I think I'll put the reference symbolic formulas in some latex-text box, giving up with the initial idea to keep them in the CAS view.

© 2021 International GeoGebra Institute