Course textbook and companion reader
The Math of Circles, Waves, and Everything That Repeats
Two books, and four ways in.
The course textbook and its history companion, each free to read in a browser and free on Apple Books.
Course Textbook
The Math of Circles, Waves, and Everything That Repeats
Trigonometry starts with a triangle you can measure and ends with a wave that repeats forever. This textbook walks that whole path in four units: Triangle Geometry, The Unit Circle, Periodic Functions, and Solving Trig Equations.
Companion Reader
From Chord to Sine to Wave
Trigonometry did not begin as the subject you were taught. It began as a table of chords, built so astronomers could say where a planet would be. This is the story of how that table became the sine, and how the sine became the wave.
The rest of the shelf
Every one of them is free, opens in a browser, and keeps working with the wifi off.
