The study of trigonometry (as well as any mathematical subject) should be based on a solid understanding of the basic ideas, and memorization should be kept to a minimum. For that reason we oppose using the now fashionable "sohcahtoa" approach to trigonometry, which obscures the fundamental ideas.
YouTube rep advised me me to add a paragraph to each upload. Here it is: Jane, a retired university math teacher, started this volunteer project in April 2009. Positive feedback from wonderful viewers worldwide keeps her motivated. Jane is a strong advocate of reading music. She made unconventional sight-reading lessons that simplifies reading music.