几何课本中常有一些典型题,如果将这些典型题进行适当的变换,例如改变题目的已知条件或结论,可以得到一系列相关面有意义的题目,一些考试或竞赛中常常会出现根据课本题目改编的试题.下面我们就课本上一题给出一些变形. There are often some typical questions in geometry textbooks. If these typical questions are appropriately transformed, for example, changing the known conditions or conclusions of the questions, a series of relevant topics with meaningful meanings can be obtained. Some examinations or competitions often appear on the basis of textbook questions. Adapted test questions. Below we present some variations on the textbook question.