研究几何图形时,若在一定范围内改变其中一个或几个元素的位置,一般说来,图形的性质也会发生变化。但是也有可能图形的某些性质不改变,我们将这些不变的性质用数量关系、表示出来,就成为几何中的定值问题。有些定值问题,实际上是某一族几何图形的共性。 When studying geometric figures, if you change the position of one or a few elements within a certain range, generally speaking, the nature of the figure will also change. However, it is also possible that some of the properties of the graph do not change. We express these invariant properties in terms of quantitative relations and become fixed values ​​in geometry. Some valuation problems are actually the commonalities of a certain family of geometric figures.