This document introduces the SOH CAH TOA mnemonic for remembering the definitions of the trigonometric ratios sine, cosine, and tangent. It states that SOH CAH TOA is a trigonometric ratio and defines sine as opposite over hypotenuse, cosine as adjacent over hypotenuse, and tangent as opposite over adjacent. It then provides examples of using trigonometric ratios to solve for unknown angles and sides of right triangles.