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How to get the roots of an equation

Hallo. I am dealing with a very simple problem of non-linear magnetic circuit. Thus, by solving the equation that gives me point of operatio, that is the real root, I cannot have it to manipulate for the sequence calculus. Would someone help me, please ?

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POSTED BY: Sergio Cabral
5 Replies

Thank you so much, Paul ! It does work !! Scabral

POSTED BY: Sergio Cabral
Posted 9 years ago

Hi Sergio I think I know where you want to go with this. I'm sure there are more elegant ways to achieve this but this is what I do to extract results for further use. If we set the calculation like this

p = Solve[0.1333*H*H/(95*95 + H*H) - k*(Nesp*Ix - H*lm) == 0, H, 
  Reals]; p = FromDigits[H /. p]

the variable p is now your new result, thus

167.894

we can now use this in the follow up

(0.133*p^2)/(95^2 + p^2)

giving this 0.100745

Hope this helps a little

Paul.

POSTED BY: Paul Cleary
Posted 9 years ago

You can also remove the warning messages by using equivalent fractions instead of the decimals, for instance use 2/15 instead of 0.1333333. Use Rationalize[0.1333333333] to do that for you. All instances of decimal must be removed before the message disappears.

Paul

POSTED BY: Paul Cleary
Posted 9 years ago
Reduce[0.1333*H*H/(95*95 + H*H) - k*(Nesp*Ix - H*lm) == 0, H, Reals]

returns

H == 167.894

but that will not always work without warnings or errors from some problems

POSTED BY: Bill Simpson

Thank you, Bill and Paul. But I think my question was not so clear. I mean, what if I want to take that value for H to continue with a sequence of calculation ?For example , B=H*H ? Scabral

POSTED BY: Sergio Cabral
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