The diameter and the circumference of a circle correlate.

的直径与周有相互关系。

Please move counterclockwise in a circle!

请逆时针做周运动。

The envelope of moving line on the hypocycloid plane may be an epicycloid or cardioid and the...

摆线逆运动中与动切线成定角的直线,其包络是周渐开线.

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.

在上的环索线，以心为极点，周上的一点为固定点，所作出的图形！