This document discusses trigonometric ratios and their use in right triangles. It defines the three basic trig functions - sine, cosine, and tangent - which relate angles to sides of a right triangle. Sine is defined as the ratio of the opposite side to the hypotenuse. Cosine is the ratio of the adjacent side to the hypotenuse. Tangent is the ratio of the opposite side to the adjacent side. Several examples are given of calculating trig ratios and solving for unknown sides or angles in right triangles. Angles of elevation and depression are also defined.