There are three methods for tangent vector discussed in this paper.
本文指出了切线向量的三种求法。
In this paper, the tangent vector loading method and the boundary element restrain method was presented.
采用了切线矢量加载和边界单元的约束方法建立分析模型。
Then actually there are ways you can use basically differentials and constrained partials to figure out what the tangent vector to the curve is and so on.