在正方形内旋转时，始终与四边保持接触的曲线。这类曲线有时也称为滚子。
封闭凸曲线的“宽度”定义为包围它的平行线（“支撑线”）之间的距离。每个定宽曲线都是凸的。定宽曲线无论在平行线之间的方向如何，都具有相同的“宽度”。实际上，它们也具有相同的周长（巴比耶定理）。例子包括圆（具有最大面积）和勒洛三角形（具有最小面积），但存在无数个。定宽曲线可以用于特殊的钻夹头来切割方形“孔”。
推广得到定宽体。对于给定的宽度，它们不具有相同的表面积，但它们的阴影是具有相同宽度的定宽曲线！
定宽曲线
另请参阅
Delta 曲线, Kakeya 针问题, 勒洛三角形, 定宽体使用 Wolfram|Alpha 探索
参考文献
Blaschke, W. "Konvexe Bereiche gegebener konstanter Breite und kleinsten Inhalts." Math. Ann. 76, 504-513, 1915.Bogomolny, A. "Shapes of Constant Width." http://www.cut-the-knot.org/do_you_know/cwidth.shtml.Bogomolny, A. "Star Construction of Shapes of Constant Width." http://www.cut-the-knot.org/Curriculum/Geometry/CWStar.shtml.Böhm, J. "Convex Bodies of Constant Width." Ch. 4 in Mathematical Models from the Collections of Universities and Museums (Ed. G. Fischer). Braunschweig, Germany: Vieweg, pp. 96-100, 1986.Croft, H. T.; Falconer, K. J.; and Guy, R. K. Unsolved Problems in Geometry. New York: Springer-Verlag, p. 7, 1991.Fischer, G. (Ed.). Plates 98-102 in Mathematische Modelle aus den Sammlungen von Universitäten und Museen, Bildband. Braunschweig, Germany: Vieweg, pp. 89 and 96, 1986.Gardner, M. "Mathematical Games: Curves of Constant Width, One of which Makes it Possible to Drill Square Holes." Sci. Amer. 208, 148-156, Feb. 1963.Gardner, M. "Curves of Constant Width." Ch. 18 in The Unexpected Hanging and Other Mathematical Diversions. Chicago, IL: Chicago University Press, pp. 212-221, 1991.Goldberg, M. "Circular-Arc Rotors in Regular Polygons." Amer. Math. Monthly 55, 393-402, 1948.Kelly, P. Convex Figures. New York: Harcourt Brace, 1995.Rademacher, H. and Toeplitz, O. The Enjoyment of Mathematics: Selections from Mathematics for the Amateur. Princeton, NJ: Princeton University Press, 1957.Steinhaus, H. Mathematical Snapshots, 3rd ed. New York: Dover, pp. 150-151, 1999.Wells, D. The Penguin Dictionary of Curious and Interesting Geometry. London: Penguin, pp. 219-220, 1991.Yaglom, I. M. and Boltyanski, V. G. Convex Figures. New York: Holt, Rinehart, and Winston, 1961.在 Wolfram|Alpha 中被引用
定宽曲线请引用为
Weisstein, Eric W. "定宽曲线。" 来自 MathWorld--Wolfram Web 资源。 https://mathworld.net.cn/CurveofConstantWidth.html