Trigonometry is useful. If you would like to learn a bit about trigonometry, or brush up on it, then read on. These notes are more of an introduction and guide than a full course. For a full course you should take a class or at least read a book.
There are no grades and no tests for you to take, and no transcripts and no awards. There are a few exercises for you to work on, but only a few. The exercises are the most important aspect of a trigonometry course, or any course in mathematics for that matter.