文章利用射影几何方法及配极原理给出二次曲线中点弦存在性定理的证明。
In this paper, the existence theorem of midpoint chord of quadratic curve, as well as its proof, is given via methods of projective geometry and polarity principle.
二次曲线中点弦存在性问题的探讨，对二次曲线的研究有着及其重要的意义。
Problems about the existence of midpoint chord of quadratic curve is worthy of discussing in the study of the theories about quadratic curve.
用间接观测平差法分析线性回归方程，用曲线中点比较法选择最优非线性回归方程。
Linear regression equation is analyzed by using indirect error-smoothing, and nonlinear regression equation is optimally selected by using the method of comparison of mid-point of curve.
就像你看到的，只有一半轨迹被扫描，因为是从轮廓曲线中点的位置开始的，选择面，然后在俯视图中进行镜像，如下图。
As you can see, only half of the rail is swept, because the sweep starts from middle, where the profile curve is positioned. Select the surface and mirror it in the Top viewport as shown below.
由频响求解器直接得出电阻基体中点的加速度响应曲线，其仿真精度通过振动试验给予了验证。
The acceleration response curve of resistor body midpoint can be computed by direct frequency response solution, simulation precision is testified by vibration test.
直线被圆锥曲线截得弦的中点问题，是解析几何的重点和难点。
The problems about the midpoints of the chords cut by the taper curve are the most critical and difficult in analytic geometry problems.
介绍了化学点火具中点火头药剂的研制及其压力——时间曲线。
This paper introduces the development and pressure-time curves of the composition of match head on the chemical igniter.
几何约束是提高复杂曲面建模精度的重要手段，其中点与曲线是最有效的几何约束。
Geometric constraints are important means to improve the precision of complex surface modeling. Points and curves are the most effective ones among geometric constraints.
几何约束是提高复杂曲面建模精度的重要手段，其中点与曲线是最有效的几何约束。
Geometric constraints are important means to improve the precision of complex surface modeling. Points and curves are the most effective ones among geometric constraints.
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