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Solve an equation with a Piecewise function?

Pio Tyldens
Posted 7 years ago

Hello I'm new to Mathematica, though I know a few about it. I'm trying to find a group of 2 values for Piecewise function changing with x, but I constantly have a problem with Solve producing a lot of errors can you tell me where is my mistake in this ? Whole thing is in attached file, Basically its:

F(x)=Piecewise[...](x,wl,wp)
Solve[MaxValue[F,x]/MinValue[F,x]==1.15,{wl,wp}] Or
CylindricalDecomposition[1.1<=MaxValue[F,x]/MinValue[F,x]<=1.2,{wl,wp}]

So I'm trying to get wl and wp values for optimization, but certainly I'm doing something wrong, please help.

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POSTED BY: Pio Tyldens
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ok. but what exactly is your problem?
POSTED BY: Hans Dolhaine
Pio Tyldens
Pio Tyldens
Posted 7 years ago

So i used manipulate to easly change wl and wp numbers searching for proper outcome, also I changed the function a bit, yet Im not sure but it should close to 0 in hte end too but thats only my calculation problem, Thanks for Help, i add modified file if u wanna check it

Attachments:
POSTED BY: Pio Tyldens

And this is interesting as well......

Manipulate[
 Plot[ff[x, u, v], {x, -2, 10}, PlotStyle -> {Thick, Red}],
 {{u, 0}, -5, 5}, {{v, 0}, -5, 5}]

Maybe it gives a clue to the solution of the original question.

POSTED BY: Hans Dolhaine

Perhaps it may be helpful to get an impression of the behaviour of your function (as defined in the notebook attached to my last post)

Animate[Plot3D[ff[x, u, v], {u, -5, 5}, {v, -5, 5},  PlotRange -> {-10^4, 10^4}], {x, 0, 20, .1}]
POSTED BY: Hans Dolhaine

That seems to be sort of a difficult problem. I changed your functions to make sure that all parameters are reaching the actual calculation. But I too got lots of errors. So I tried to get som ideas about the magnitude of the numbers involved. Unfortunately I did not find any reasonable approximation of the solution you are looking for. See notebook. Do you have any ideas about the magnitude of wl and wp?

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POSTED BY: Hans Dolhaine
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