How to find real and complex roots for a nonlinear equation

Question

Marco Dellacasa 2021-9-21

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https://ww2.mathworks.cn/matlabcentral/answers/1458099-how-to-find-real-and-complex-roots-for-a-nonlinear-equation

评论： Marco Dellacasa 2021-9-22

Hi everyone,

I have to solve this eqution numerically:

the only variable is H and it tipically gives two complex roots and one real root, I've read that fzero is not suitable in this case, could anyone give mi any tips please?

Thank you

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Answer 1

Viranch Patel 2021-9-22

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在 MATLAB Online 中打开

For simplicity I have taken a simple function which has complex roots.

syms H
eq=H^2 + 1;
solve(eq==0,H)

You can specify your equation in H like this and this should give you the roots correctly.

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Marco Dellacasa 2021-9-22

在 MATLAB Online 中打开

Warning: Unable to solve symbolically. Returning a numeric solution using vpasolve. 
> In sym/solve (line 304)
In prova_Irvine (line 15) 
 
ans =
 
-8530666.6665264117623777679822889
 
>> 

Unfortunately it didn't work, I know a priori that usually this equation has in total 3 roots: 2 complex and 1 real, maybe the problem is that I have both real and complex roots to find instead only real or only complex roots?

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