This major unit revisits trigonometry from Geometry and expands it. Students study trigonometric ratios for any angle using the unit circle. They learn how to evaluate and graph sine, cosine, and tangent functions, including amplitude, period, and phase shift. Students also apply trigonometry to solve real-world problems involving height, distance, and periodic motion. Understanding these relationships prepares them for the more complex trigonometric identities and equations in Precalculus 12.