几何元素的正投影约束数及应用

The Constrained Degree and Application of Orthographic Projection Concerning Geometric Elements

三维空间中，几何元素点、直线、平面被其投影确定的程度，对于画法几何命题的确定性和可熔性有一定的指导意义。本文讨论点、直线、平面的正投影对其自由度的约束数，探索空间自由度的理论在解决画法几何问题中的应用。

The determinacy and solvability of problems in the descriptive geometry depend on the degreeof freedom of the geometric elements and their interrelationship.Left degree of freedom concerning geometric elements under the orthographic projection and theapplication to solving the problems in the descriptive geometry have been discussed.