This is a four page packet which covers basic trigonometry, particularly that needed for precalculus classes. The reviews and diagrams introduce the concept of radians, and the unit circle, not only explaining how to use them, but why we use them to impart a thorough understanding to students. The packet includes definitions of trig. functions, basic graphs of all six functions (along with domain and range) trigonometric identities, double angle formulas, half angle formulas, product to sum equations, and sum to product equations, along with expansions of addition and subtraction of trig functions. This packet is a great tool to introduce the information to students, or to use as reference material.