Conic Sections

The curves you get when you slice a cone are called conic sections and have many applications. Click on one for further details.

One application is that a moving particle that is subjected to an inverse square law force like gravity or Coulomb's law will follow a path described by one of the conic sections. 一个应用是，一个受重力或库仑定律这种反平方定律力作用而运动的质点，其轨迹将由一种圆锥曲线描述。

Each of the conic sections can be described in terms of a semimajor axis a and an eccentricity e. Representative values for these parameters are shown along with the types of orbits which are associated with them. 每个二次曲线都可以用半长轴a和偏心率e来描述。这些参数的代表性值如图所示，并列出了与之相关的轨道类型。

Every equation of the form

• Circle: A and C equal and not zero.
  圆：A 和 C 相等且不为零。
• Ellipse: A and C unequal but have the same sign.
  椭圆：A 和 C 不相等但符号相同。
• Parabola: Either A or C (but not both) is zero.
  抛物线：A 或 C 中有一个为零（但不同时为零）
• Hyperbola: A and C have opposite signs
  双曲线：A 和 C 符号相反