line lengh= wavelengh at 72º

does someone can explain me how to address that on how long is the line of my sub?

Hi Itay! I don't understand your question. What do you mean by "how to address that"?

Maybe you are wondering how to use this to influence your designs?
If so, what is unclear to you about it?
If line length equals the wavelength at which you have 72º of coverage, what's the question there?