补形法又称扩形法,就是根据题设条件和图形,经过观察、分析和联想,运用添加辅助线的方法,将其拓展为范围更广的、其特征更为明显、更为熟悉的几何图形,从而沟通条件和结论之间的联系,为解题开辟了新的途径和方法. Complementary method, also known as the expansion method, is based on the conditions of the questions and graphics, through observation, analysis and association, using the method of adding auxiliary lines to expand it into a wider range of features more obvious and more familiar The connection between geometrical conditions and communication conditions and conclusions opens up new ways and methods for problem solving.