《中学生数学》2 0 0 1年 1 0月上期所发表的《用定义证明直线和平面平行的判定定理》是误解、误用平行公理之一例 .为了便于说明 ,先将该文证法照抄如下 :图 1已知 :直线ａ 平面α ,直线ｂ α ,ａ∥ｂ(如图 1 ) ,求证 :ａ∥α .证明　设点Ｐ是平面α内的任意一点 ,则Ｐ∈ｂ The “Demonstration Theorem for Proof Lines and Plane Parallelism with Definitions” published in the “Middle-school students mathematics” issue in the previous month of October 2001 is an example of misunderstanding and misuse of parallel axioms. For ease of illustration, copy the documentary evidence as follows: : Figure 1 is known: line a plane α, line b α, a ∥ b (as shown in Figure 1), verify: a ∥ α . Prove that the set point P is any point in the plane α, then P ∈ b