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

摆运动中与动切成定角直,其包络是圆周渐开.

Construct rotating nephroid and three-cusped epicycloid while remaining orthogonal to each other.

作旋转肾脏和旋转外摆，且彼此维持正交。