平面斜截正圆锥截交线为椭圆时投影曲线分析

The projection curve analysis when a plane cuts off a circular cone with an ellipse section line at an oblique angle

讨论了平面斜截正圆锥，截交线为椭圆时，其水平投影及侧面投影能否为圆的问题．分析了椭圆的水平投影其长、短轴方向不随斜截角度的改变而改变的投影特性，以及侧面投影为圆时，截平面应满足的条件．

This paper discusses whether the horizontal projection and profile projection will be a circle when a plane cuts off a circular cone at an oblique angle with an ellipse section line. It is determined that the direction of both the major and minor axis of ellipse’s horizontal projection will keep constant. In addition the paper provides with the conditions which the section plane meets when its profile projection is a circle.