tangent plane arc-length method切面弧长法
lower tangent arc下切弧
upper tangent arc上正切晕弧
tangent arc motion切向弧线位移
vertical tangent arc垂直珥
u er tangent arc上正切晕弧
Tangent Arc Intent Zones切线弧的目标区域
Tangent to This Arc此
upper r tangent arc上正切晕弧