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式子zx±zy=1是一个较为复杂的比例式,是基本比例式zx=my的变形.对这类题的证明学生颇感困难,为此,本文通过例题介绍几种形如“zx±zy=1”类问题的证明方法,仅供参考.图1题目如图1,正△ABC内接于⊙O,P是劣弧BC上任意一点,PA与BC交于点E.求证:1PB+1PC=1PE.策略1:“移项、合并”?
The formula zx±zy=1 is a more complex proportion formula, which is a variant of the basic proportional formula zx=my. It is difficult to prove students of this type of questions. For this reason, this article introduces several forms such as “zx±. The proof method of zy=1” problem is for reference only. Figure 1 title is shown in Figure 1. Positive △ABC is inscribed with ⊙O. P is any point on the bad arc BC. PA and BC are crossed at point E. Proof: 1PB +1PC=1PE. Strategy 1: “Transposition, Merge”?