astroid

基本解释

Construct the astroid as the envelope of a family of lines.
作由线族包络线所形成的星状线.
Construct an animation of three concurrent tangents of the astroid.
建构一动态绘图：展示星状线共点的三切线。
Construct an animation showing the inscribed ellipse of an astroid.
建构一动态绘图：展示星状线的内切椭圆。
Obviously, a line of astroid nebula is a result which the star old age evolves.
可见，行星状星云是恒星晚年演化的结果。
Show how a deltoid of maximal size slides inside a stationary astroid.
在固定不动的星状线内，有一个最大的三角线在其间滚动。