# what is the meaning of (left half plane of roots)?

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ali temsah on 14 May 2022
Commented: Voss on 14 May 2022
the roots
b=
-0.3642 + 0.7125i
-0.3642 - 0.7125i
0.3642 + 0.7125i
0.3642 - 0.7125i
does it means only the real roots only?
or
the first two rows?

Voss on 14 May 2022
Edited: Voss on 14 May 2022
The left half-plane refers to the part of the complex plane where the real part is less than 0 (or <= 0 if you want to include the imaginary axis).
b=[
-0.3642 + 0.7125*i
-0.3642 - 0.7125*i
0.3642 + 0.7125*i
0.3642 - 0.7125*i]
b =
-0.3642 + 0.7125i -0.3642 - 0.7125i 0.3642 + 0.7125i 0.3642 - 0.7125i
b(real(b) < 0)
ans =
-0.3642 + 0.7125i -0.3642 - 0.7125i
In this case, the first two elements of b (which is the first two rows) are in the left half-plane, yes.
##### 2 CommentsShowHide 1 older comment
Voss on 14 May 2022
You're welcome!

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