In this paper, we make use of the properties of the umbilic to research circle Section question of quadric in 3-dimensional euclidean space.We give the equations of these circle sections.

• 文章利用脐点的性质研究了二次曲面的圆截口问题，并给出了与二次曲面交线为圆的圆截口的方程的一种求法。