说明：  用VB开发的简单二维绘图程序，特别推荐其中的关于图形几何算法，包括点、直线、圆、圆弧之间的距离、交点、切点。
(VB development of simple two-dimensional mapping procedures, in particular the recommendation of the graphic geometric algorithms, including point, line, circle, arc gap between Nodal, the cut-off point.)