strophoid
1. Definition : A strophoid of a circle with the pole O at the centre of the circle and the fixed point P on the circumference of the circle.
定义:在圆上的环索线,以圆心为极点,圆周上的一点为固定点,所作出的图形!
2. oblique strophoid
斜环索线 斜环诉
3. right strophoid
正环索线