Construct an animation displaying a nephroid sliding along three fixed concurrent lines meeting at 120 degrees. 建構一動(dòng)態(tài)繪圖。展示腎臟線(xiàn)的滾動(dòng)，沿著(zhù)共點(diǎn)及間隔120度的三條直線(xiàn)。
This paper discusses the relations between concurrent lines theorem and collinear points theorem of the projection geometry, and obtains their duality relation and equivalence relation. 對射影幾何中的共點(diǎn)線(xiàn)（共線(xiàn)點(diǎn)）定理之間的關(guān)系進(jìn)行探討，給出它們有關(guān)的對偶關(guān)系和等價(jià)關(guān)系。
