Trigonometric functions were discovered by the Greeks, Egyptians and other ancient cultures more than 2000 years ago. As they sought to combine the models of right triangles and circles their efforts would result in a precise method of measuring and describing angles as they change over time.  Today any science that seeks to track a precise angular movement uses the ideas and principles of trigonometric functions. For this reason, mastering trigonometry is often seen as a critical step in becoming a meaningful contributor to the world of STEM.