组合体的投影作图，一直是学生在学习画法几何和工程制图当中的一大问题。
The projection drawing of assembly has been a big headache for stu dents when learning techniques of geometry drawing and engineering drawing.
用圆弧投射法解决圆锥曲线与其它空间几何要素的相互位置问题，可使作图更为简练、精确。
By using circular arc project, the relative positions of the conic curves and other spatial geometrical elements can be solved for simplified and precise drawings.
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 .
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