# Question about how complex poles are derived

• April 4th 2011, 08:02 AM
hunterage2000
Question about how complex poles are derived
Can someone please look at the attached pdf and tell me how the top part is siomplified to the bottom.
• April 4th 2011, 08:07 AM
FernandoRevilla
$(2\zeta w_n)^2-4w_n^2=4w_n^2(\zeta^2-1)$ etc.
• April 4th 2011, 08:18 AM
hunterage2000
Thank you mate