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V
vveeran4-Participant
4-Participant
May 2, 2016
Solved

Error in computing the polyroots

  • May 2, 2016
  • 3 replies
  • 2503 views

Hi all,

I want to compute polyroots for the example program which I attached below.

But, I am getting some error in computing the polyroots.

Please help me to find out roots for my example program.

Also, I need to plot Real and Imaginary part of poles of the

given example program.

Best answer by -MFra-

I'm sorry! I provide immediately. But also the F. Kolepp solution is of some merit.

About your question:

1) When looking for a symbolic solution, you have to reset all the variables and constants involved. Otherwise you will not get a symbolic result, but a numeric result.

2) That is the symbolic solution of the equation included in the "Given-Find" block.

3) simply replace the quadratic equation with the third degree where there is the symbolic operator "solve".

Bye

3 replies

W
Werner_E25-Diamond I
25-Diamond I
May 2, 2016

polyroots is a numeric function bit your coefficients include the LambertW Function which in Mathcad is only known by the symbolics. Thtas the reason for the error.

V
vveeran4-ParticipantAuthor
4-Participant
May 2, 2016

Dear Werner,

Could you please correct the error of my program

and find the roots of my given program,

So that it will be helpful to me.

Thanks.

-
-MFra-21-Topaz II
21-Topaz II
May 2, 2016

I would do so, I do not know if that's what you want

Error in computing.jpg

V
vveeran4-ParticipantAuthor
4-Participant
May 2, 2016

Dear F.M,

Thank you for your reply.

That is what I needed.

Could you please attach the code.

could you please explain,

why did you initialized like this,

gamma1= gamma1, x=x , beta1=beta1

what is the meaning of this,

ans(v)->LambertW((v^2*beta1/20)v + beta1(v)*gamma1(v)) / beta1(v)

Similarly,

If suppose I have cubic roots like,

a3(v) s^3 + a2(v)s^2 + a1(v)s +a0(v) = 0

where a3(v), a2(v), a1(v) and a0(v) are coefficients.

How to compute the roots by using the above procedure.

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
May 2, 2016

If you convert v from a range to a vector you can make your sheet work.

See attached.

V
vveeran4-ParticipantAuthor
4-Participant
May 3, 2016

Thank you all

for your replies.

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