The relationship between polhode and herpolhode of the instant center of a rigid body when it makes a plane paraller motion is presented.

给出了刚在平面平行运动时，刚极迹与空间极迹间关系一种证明方法.

A certification method to the relationship between polhode cone and herpolhode cone is given when the rigid body is in a fixed point motion.

摘要给出了刚定点运动时极面与空间极面间关系一种证明方法。