Hi Allan,
Oh yeah... I could write a book on bisecting and trisecting arcs in order to layout because I used to teach the very same method of layout many moons ago when they still taught you how to fit and how to make your own drawings without the use of some form of CAD... It's good to see that there are still a few like yourself that still do incorporate these important skill sets for the students who want to become a true welder/fabricator as opposed to a glorified rod burner who whines if they even have to pick up a grinder for crying out loud!!!
At first the students which were of a demographic where math was only thought to be used to make money illegally and trigonometry was a foreign language, the kids were initially intimidated... And yet if the correct approach of identifying immediately what they could do with these skill sets including how much greater worth they will be once they become competent with using these layout methods and how precise their results are reproduced... Most of them jump in with both feet wanting to learn these tried and true methods of layout, and the ones that are still sort of hesitant usually get in a very short period of time because the key to successfully teaching these methods is by the students using them to construct their first fabrication as opposed to just sitting in the class struggling from trying to stay awake and paying attention to the instructor which is doomed to failure almost as fast as it takes to finish the first week!!! By showing them how "magical" theses skill sets are when performing layouts, in no time they will be showing this to their friends and family, or just about anyone else that they want to impress with these new found skills... That's when you know you did your job and it's very satisfying to witness!
It's very refreshing to see that there are some folks like yourself still teaching these skill sets Allan... Because those students that become competent with using these skills will have an edge over those who are not taught this... And their value as an employee will increase with having competency in using the greater diversity of various skill sets besides these...In affect, they will be more valuable, and productive employees and can also take these skills to maybe venture into their own business one day also... The sky is the limit yet not for long because even that barrier is soon to be shattered also!
Respectfully,
Henry