Hi! I am trying to solve a textbook problem without any success. Fortunately, I found someone that solved it but there is one step that I don't get. Here is a figure showing the problem : https://ibb.co/koatCa First, we have (I get this part since I found a similar use of it in the book): X/b=1/|1-(ω/ωn)2|=0.15/0.10=1.5 And the thing I can't understand is how the person get the following numbers: For ω<ωn : ω/ωn= 0.577 For ω>ωn: ω/ωn=1.291 Anyone who can explain? Thanks!