The site works through a point system, as you will earn points for donating items.
该网站使用点数，你可以通过捐赠物品获得点数。
This paper discusses the graphic problem of ellipse normal through a point outside the ellipse. Concluded are the unsolvability of geometric graphic method to solve this problem .
对过椭圆外一定点的法线作图问题作了探讨，指出了几何作图法的不可解性。
This paper discusses the graphic problem of ellipse normal through a point outside the ellipse. Concluded are the unsolvability of geometric graphic method to solve this problem .
对过椭圆外一定点的法线作图问题作了探讨，指出了几何作图法的不可解性。
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