#set  heading(numbering:  "1.")
=  Routh-Hurwitz
== If a pole exist in  left  semiplane then  it's  a unstable system

==  Poles  must  appear in even lines for the Routh-Hurwitz

==  Signal  change  overwrite every other "minor rule"  

==  Signal change implies  pole  in   right semiplane

==  Every  pole  in the  imaginary  axis  must have a  counterpart 
$->$  multiplicity  of  2

==  Null line appears only if  a polynomial  divides another
$->$  always appear in odd  degree  polynomial
#line(length: 100%)
#line(length: 50%, angle: 90deg)
