Trigonometry is essentially the study of how lengths vary compared to the rotations or angles that create the length. Thus, this unit begins with careful development of essential angle and rotation terminology, including reference angles, quadrant work, and radian angle measurement. The sine and cosine functions are then defined in terms of the unit circle. Graphs of sine and cosine are developed from the simple to the complex. Important terminology, such as amplitude, frequency, period, and midline are reinforced through real world applications. The four trigonometric ratio functions are then defined with their basic characteristic and graphs examined.