NavList:

Lars, I just received and printed the files you sent, and I'll now go through your derivation of the formula for longitude. But before I do it, I'd like to let you know that I'm very grateful to you for taking the time to write it out. As for the formula for latitude, you reminded me of a phrase frequently found in college maths textbooks: "The second part of the proof is left as an exercise for the student".                                                                                                                                                                         

Thanks, Rafael