Review: Trigonometry: Notes, Problems and Exercises

Trigonometry: Notes, Problems and Exercises by Roger Delbourgo
My rating: 2 of 5 stars

...Spherical trigonometry inspires the cover art of this text, yet that topic only arises in the sole appendix. While that appendix is larger than any chapter by a few pages, this text is one of planar trigonometry. That focus is essential and a conscious direction here. I informally poll students coming out of trigonometry asking, “Is trigonometry about the unit circle or triangles?” I am disappointed so many I meet leave their first encounter with this subject assuming the unit circle is “the whole point”, as I have been told. The unit circle does not even make a cameo appearance in this book, and indeed while it is a power tool to exhibit properties and functions, it is not required. The approach here is a welcomed focus on planar triangle geometry that builds nicely to the Nine Point Circle and other topics often crowded out of introductory courses due to the time and attention paid to the unit circle’s possibilities.
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