Otto J. Karst, Semi-Complex Functions and Their Graphs, Mathematics Magazine, Vol. 35, No. 5 (Nov., 1962), pp. 282-288 ...

Revise working with the graphs of trigonometric functions for your National 5 maths exam with Bitesize Scotland interactive practice quizzes covering feedback and common errors.

This rule regularly shows its face with Functions & Graphs on paper 1. Don't forget your maths sets because you could be asked to measure a few lengths on the diagram given.