Precalculus by Richard Wright

Triangles are a very stable and strong shape for construction. Truss bridges are made from triangles and designed for strength. Trigonometry studies triangles, but its applications are wide ranging. For example, the sound of the train's horn can also be modeled by trigonometry.

4-03 Right Triangle Trigonometry

4-04 Right Triangle Trigonometry and Identities

4-05 Trigonometric Functions of Any Angle

4-06 Graphs of Sine and Cosine

4-07 Graph of the Other Trigonometric Functions

4-08 Inverse Trigonometric Functions

4-09 Compositions Involving Inverse Trigonometric Functions

4-10 Applications of Right Triangle Trigonometry