仅当两个圆柱孔直径相等时，相切发生在圆柱中心平面。
相切是由曲面边界的最初两个控制点控制的（假设这些点在一条线上）。
初亏：月球由东缘慢慢进入地影，月球与地球本影第一次外切。
此种测量方法非常适合于微小、易形变等接触测量难以准确测量的机械零件的参数检测，具有广阔的应用前景。
提出了一种基于最小二乘拟合的改进算法，来进一步确定角点和切点，并对轮廓分段识别。
1·Create the surface using sweep 2 rails with the tangency option on. To achieve tangent option you will have to build the surface in parts.
创建表面使用扫描第2轨与相切选项。为了实现切线选项，您将必须建设中的表面部分。
2·With the Lagrange multiplier method, the minimum distance of the center of a circle and a quadric surface was provided and the tangency condition of curve and surface was given.
利用拉格朗日乘子法求解二次曲线和二次曲面之间的最小距离，给出了曲线与曲面相切的条件。
3·The sealing ring cross section is V-shaped, and inner groove between two side edges composed the V-shaped is formed by tangency of two arcs with different radiuses.
密封圈的横截面呈＂V＂字形，构成＂V＂字形的两个侧边条之间的内槽由两个半径不等的圆弧相切而成。
4·Tangency is controlled by the first two control points from a surface boundary, assuming that these points lie in one line.
相切是由曲面边界的最初两个控制点控制的（假设这些点在一条线上）。
1·Moon enters penumbra: instant of first external tangency of moon with the penumbra.
半影食始：月球刚刚和半影接触，这时肉眼觉察不到。