OFFER (One-Figure-Facilitates-Every-Relationship)for Trigonometric Functions

This article describes an approach that uses a single figure to illustrate all six trigonometric functions, their fundamental identities, and the law of cosines. We name this method OFFER (one-figure-facilitates-every-relationship) for the convenience of mathematics teaching. The article also describes the SPORT (story-picture-observe-review-tell) approach to effective mathematics learning.