Dear all, I am following Warren F. Phillips' book "Mechanics of Flight" (2nd edition) and am trying to code the numerical lifting line method outlined by him starting on page 96 of Chapter 1. I will write the code in Matlab, but what is preventing me from doing so is a few variables within the said method which I am confused about how to find. Variable number one is dli, which is defined as the "directed differential vortex length vector"; the boundary of my knowledge of vector calculus is differentiating vectors. Now, the method does not require anything beyond that- but I do not know what the vortex length vector even is, and how one finds it. Question number two is about Newtons method. What is a relaxation factor? As I write my code, I might have more questions and I will probably ask them here. For now, I would appreciate your help in explaining to me what variable number one is/how it is found! For reference, variable number one is cited to come from Saffman 1992- I have the book, but cannot find anything on the variable in it (300+ pages, non-searchable format). The method itself is referenced to come from a more detailed account on it in Phillips and Snyder 2000. THANK YOU!