在平面上繪製三個圓，其中任何一個圓都沒有完全包含在另一個圓內，並繪製每對圓的公外切線。然後，三對切線的交點位於一條直線上。
蒙日圓定理有一個三維類比，它指出由四個球體（每次取兩個）定義的圓錐的頂點位於一個平面上（當圓錐在球體的頂點同一側繪製時；Wells 1991）。
蒙日圓定理
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圓-圓 切線， 圓 切線使用 探索
參考文獻
Bogomolny, A. "Three Circles and Common Tangents." http://www.cut-the-knot.org/proofs/threecircles.shtml.Bogomolny, A. "Monge via Desargues." http://www.cut-the-knot.org/Curriculum/Geometry/MongeTheorem.shtml.Bogomolny, A. "Monge via Desargues II." http://www.cut-the-knot.org/Curriculum/Geometry/MongeDesargues.shtml.Coxeter, H. S. M. "The Problem of Apollonius." Amer. Math. Monthly 75, 5-15, 1968.Graham, L. A. Problem 62 in Ingenious Mathematical Problems and Methods. New York: Dover, 1959. Ogilvy, C. S. Excursions in Geometry. New York: Dover, pp. 115-117, 1990.Petersen, J. Methods and Theories for the Solution of Problems of Geometrical Constructions, Applied to 410 Problems. London: Sampson Low, Marston, Searle & Rivington, pp. 92-93, 1879.Walker, W. "Monge's Theorem in Many Dimensions." Math. Gaz. 60, 185-188, 1976.Wells, D. The Penguin Dictionary of Curious and Interesting Geometry. London: Penguin, pp. 153-154, 1991.在 中被引用
蒙日圓定理請引用為
Weisstein, Eric W. "蒙日圓定理。" 來自 Web 資源。 https://mathworld.tw/MongesCircleTheorem.html