The mathematician explained the properties of a tangent line.

数学家解释了切线的性质。

Slope of the tangent line

切线的斜率

The mathematical equations of theoretical contour of cam and its tangent line and normal line were derived.

推导出了凸轮理论廓线及其切线与法线的数学方程；

So, if I draw the tangent line to this slice, x then the slope will be partial f of partial x.

如果画出这个切片的切线，那么斜率就是∂f/∂

Adopt the sloping cutting craft, cutting along the tangent line of sheet's mid point on Z .

在切割工艺上采用倾斜切割的方法，沿分层板造型曲面中点的Z向切线进行切割。