"Trigonometry" is a free, open-source textbook on trigonometry, with over 1000 pages, covering the subject from basic concepts to advanced topics.

The book covers angles and triangles, trigonometric relationships, the unit circle, sine, cosine, and tangent functions, graphs and their transformations, radians, solving triangles, the sine and cosine theorems, trigonometric identities and equations, inverse trigonometric functions, and formulas for the sum, difference, and double angle.

Later chapters also cover vectors, the dot product, polar coordinates, and complex numbers in polar form.

Each section contains numerous exercises, making the textbook particularly useful for reinforcing theoretical knowledge through practical application as you progress through the material.

https://louis.pressbooks.pub/trigonometry/