Sorry if this has been posted before. If so, please direct me to the previous version so I can delete it.
I saw this PDF of Hall & Knight's 1906 "Elementary Trigonometry" (archive.org link).
I use Khan Academy as a spare and a resource, but I see that this PDF has more advanced trigonometry, like csc and inverse. In Khan Academy well tell me on algebra 2 section and pre-calculus section trigonometry csc, cot, and its inverse.
I was wondering whether or not I should finish Khan Academy first or after I do pre-calculus section before I do pre-calculus then read Hall & Knight and other trigonometry non-calculus-type PDFs. I know I need to be fluent in trig, algebra, etc, to be the best in calculus I can be. What should I do?
Knight and Hall's Elementary Trigonometry is a very good book (and it's free!), but you could probably use any book in tandem with what you're learning from the Khan Academy.
A book that might be more advanced for beginners is Loney's Trigonometry, which also incorporates complex numbers and their functions into elementary trigonometry. I would stick with the Khan Academy first, then if you feel you've mastered that, go for Knight and Hall.