cubic spline(s)

例句：

1. 1.The cubic spline function is used to fit the data points closely.
   立方插值多项式用于将数据点紧密地拟合。
2. 2. The cubic spline curve is smooth and has a high degree of accuracy.
   立方插值曲线平滑且精度高。
3. 3.The cubic spline function is widely used in engineering for its ability to accurately fit complex shapes.
   立方插值多项式在工程中被广泛使用，因为它能够准确地拟合复杂的形状。