来看一下这一点，这里双曲线和圆刚好接触的地方，首先，我不知道我要看的是圆上面的哪一点。
If you look at this point where the hyperbola and the circle touch each other, first of all, I don't know which circle I am going to look at.
切线是一条直线，刚好接触到曲线，所以跑切线是从一个弯道跑到另一个最短的距离。
A tangent is a straight line that just touches a curve, so the concept of "running the tangents" is to run the shortest distance possible by running straight from one curve to the next.
为了增加接触面积并承受较大载荷，滚珠在内外环的曲线槽内滚动。
To increase the contact area and permit larger loads to be carried, the balls run in curvilinear grooves in the rings.
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