应用第二笛沙格定理作二次曲线

为了使二次曲线的作图更简便，文章以第二笛沙格定理和对合定理为基础，提出了一种新的作图方法。全文不仅详细论述了有关原理和作图方法，并以一机构实例解释了作图方法的应用。该方法的特点是在整个图解过程中，所有的作图线一般为互相平行或垂直的直线，使作图更简便且精确度有所提高。此方法亦可为类似的机构轨迹作图提供参考。

Construction of a conic by means of the Second Desargues Theory

Based on the Second Desargues Theory and involution theory,a simple drawing method for a conic is presented.The new method and relative principle are introduced in detail,and a mechanic example is given to show its application. The advantage of the new method is that all the drawing lines are parallel or perpendicullar to each other on the whole,so it is more simple and accurate.The proposed method is also helpful for similar drawing of mechanic path.