I've been relearning trigonometry lately by myself for navigation and astronomy; not for work, just curiosity I guess. One book I've really enjoyed is Heavenly Mathematics by Van Bremmelen. It's a spherical trig textbook, but it's written by a math historian who describes how trigonometry was gradually developed over human history and he discusses its early proofs, methods and applications. I have to confess that the historical approach has really helped me develop a more complete mental picture and appreciation of the math itself. Understanding the "how" and "why" of its development, and seeing the early practical need and implementation for some of this stuff has made the topic a lot more engaging.
It seems like you'd get a lot deeper understanding by doing it that way, and be much more able to adapt the knowledge to the real world, vs only knowing how to solve problems in the exact form they were presented to you. I had so many semesters of undergrad math, did fine, but feel like I took basically nothing from it.
This is a very entertaining hobby to have. Wishing you a lot of fun.
Next stop, making sundials and reading astrolabe.
I was so surprised to know that Chaucer had such interest in the workings of an Astrolabe. It's not much of a surprise if you think that Astrolabe were the pocket GPS, pocket watch, pocket star chart of those times.
I used to love browsing back issues of journals on school/college Mathematics by volume using /scimag path of old libgen. Journals such as
American Mathematical Monthly
Mathematics Gazette
College Mathematics
Mathematical Intelligencer
and so on
The interface let you navigate to a journal of choice, say Nature then choose an year, volume and number. Then you could read the articles in that issue.
Scimag is no longer supported on the new libgens. However, one could make do using their Series search feature. This feature is still supported in name, however no article shows up.
If anyone knows of a work around would love to know.