波利亚曾说:“拿一个有意义但又不是复杂的题目去帮助学生发掘问题的各个方面,使得通过这道题就好像通过一道门户,把学生引入一个完整的领域.”图1引例人教版《数学八年级上册》第50页的例1:如图1:在ΔABC中,AB=AC,点D在AC上,且BD=BC=AD,求ΔABC各角的度数.这道题就是一道有意义但不复杂的题,我们可以在各个方面挖掘,把学生引入一个完整的领域.解∵AB=AC,BD=BC=AD,∴∠ABC=∠C=∠BDC,∠A= Polya once said: “Taking a meaningful but not complicated topic to help students explore all aspects of the problem, so that passing this question is like using a portal to introduce students to a complete field.”“” For example, in the example on the 50th page of the first edition of Mathematical Year 8 of the Illustrator: Figure 1: In ΔABC, AB=AC, point D is on AC, and BD=BC=AD, find the degree of each angle of ΔABC. The question is a meaningful but not complicated question. We can dig in every aspect and introduce students into a complete field. Solution AB=AC, BD=BC=AD, ∴∠ABC=∠C=∠BDC, ∠ A=