现在，假设曲面上有两条相交切线，那么这两条切线可以确定一个切平面，我们来看看这个平面是怎么搞出来的。

Now, if I have two lines tangent to the surface, well, then together they determine for me the tangent plane to the surface. Let's try to see how that works.

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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。

The problem of attaining the tangent equation of a certain point on a quadratic curve is basically solved in plane analytical geometry.

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其次，基于CR列式法推导出了大旋转小应变空间杆单元及平面梁单元的内力矢量及切线刚度矩阵；

Then, based on the CR formulation, the internal force vector and tangent stiffness matrix of large rotation and small strain space bar and plane beam element are deduced.

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