Cavanagh (2008) engaged students with hands-on activities involving tangent ratios before formally introducing trigonometric functions. As echoed by Bressoud (2010), Weber (2005) introduced circle trigonometry before triangle trigonometry. He asked students to estimate the results of trigonometric functions, and posed questions that required them to reason about these functions. Thompson, Carlson, & Silverman (2007) used probing questions to help teachers realise the necessity of measuring an angle by its subtending arc length, had them use a string having the same length as the radius to measure angles and estimate sine and cosine, and used another set of questions to help them see that this angle measure leads to a coherent system of meanings in trigonometry. In order to alleviate the aforementioned problems, we propose in this article an alternative instruction that centres around Earth geometry, a topic occupying a major portion of Unit 4, Topic 3: Time and Place 2 of Essential Mathematics in the ACARA (2010) draft. Being included in Essential Mathematics confirms its importance and usefulness in making sense of the world. While reading the article, keep in mind that it is not intended as standalone instruction in trigonometry, as it is based on our experience of supplementing the main lesson, and that it can be adopted partially, depending on the curriculum. As pointed out by the late Ralph P. Boas, Jr. (1912–1992): “there is not time for enough practice on each new topic; and even if there were, it would be insufferably dull … he gets this practice in less distasteful form by studying more advanced mathematics” (Boas, 1957). At the very least, our instruction provides students with necessary practice based on real-life situations and prepares them for more advanced courses. In the next section, we present the visual aids to help students visualise the geometry of the Earth, followed by the instruction concerning angle measure, which is the foundation for the instruction in the remaining sections. We conclude our instruction with a method of finding the shortest distance between two points on the surface of the Earth (the great-circle distance