Incorporating special points procedure and the selfcontained subroutine,the range of application of the extended Huckel theory is extended to ionic system.

Moreover,we propose an approximate computation method that combines the Fourier series expansion method with the motion equations at special points.

When solving the intersecting curve formed by a cylinder going through a cone with their two axles at right angle,most of the current textbooks only provide methods which approximate the position of the special points.

Drawing methods of determining special points in the intersection of two surfaces of revolution.;

The authors propose an approximate computation method which combines Fourier series expansion with governing equations of motion for special points.

To determine the special points in intersecting lines of swing solid, especially those points in non-gathering intersecting lines, the paper synthetically utilized basic methods and new methods of circle-marking with projected ellipse to make out special points in intersecting lines and so offered basis to determine new intersected lines for different types of pipelines.

It is the key that to draw the shadow is to find several particular points of the shadow outline.

In the drawing of interseCting line,the determination of particular points on the intersecting line is most essential.