The problem of attaining the tangent equation of a certain point on a quadratic curve is basically solved in plane analytical geometry.
平面解析几何对“求过二次曲线外的点所引曲线切线的方程”的问题，未给出一般的方法和公式。
Equation about isometric polygon curve is set up with differential geometry theory. The curve is proved to be convex curve which the distance between any parallel tangent lines is equal.
应用微分几何理论，导出了等距曲线的方程，证明了它是具有任意两条平行切线之间距离都相等的卵形线。
The application of tangent-initial-displacement method in solving fabrication geometry is introduced.
介绍了切线初始位移法在求解制造线形中的应用。
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