Delta-K,  Feature Articles,  Volume 40, Issue 2

On Circumscribed Circles

Journal of the Mathematics Council of the Alberta Teachers’ Association

Volume 40 Issue 2, September 2003

62 – 65

On Circumscribed Circles

David E. Dobbs

My recent article (Dobbs 2003) proposed some enrichment material for the typical precalculus course by developing several methods to study angle bisectors and inscribed circles of triangles. It seems natural to ask if the subject of circumscribed circles of triangles can also provide enrichment material for precalculus. This article shows how that may be done. The insight that such coverage is possible at the precalculus level is not new. For instance, Smith’s (1956, 101) classic treatise includes an exercise asking for an equation of the circumscribed circle of a given triangle. Because Smith’s text does not suggest a method to work that exercise, it is of some interest to find several such methods, and I do so here.