The secant caustic of a planar curve M is the image of the singular set of the secant map of M. We analyze the geometrical properties of the secant caustic of a planar curve, i.e. the number of branches of the secant caustic, the parity of the number of cusps and the number of inflexion points in each branch of this set. In particular, we investigate in detail some of the geometrical properties of the secant caustic of a rosette, i.e. a smooth regular oriented closed curve with non-vanishing curvature.

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平面曲线的割线焦散的几何形状

平面曲线的割线苛性中号是单数集的割线的地图的图像中号。我们分析了平面曲线割线焦散的几何特性，即割线焦散的分支数、尖点数的奇偶性以及该集合中每个分支的拐点数。特别是，我们详细研究了玫瑰花结割线焦散的一些几何特性，即具有非零曲率的光滑规则定向闭合曲线。