笔者有幸参加了2015年安徽省滁州市中考数学试卷的阅卷工作,对所阅第20题感触颇深,现将阅卷过程中的发现与感悟撰写成文,以期与同行共同探讨.题目20.在⊙O中,直径AB=6,BC是弦,∠ABC=30°,点P在BC上,点Q在⊙O上,且OP⊥PQ.(1)如图1,当PQ∥AB时,求PQ的长度;(2)如图2,当点P在BC上移动时,求PQ The author had the privilege of participating in the examination of the mathematics examination paper for the entrance examination of Chuzhou City, Anhui Province in 2015. He was deeply impressed by the 20th question he read. He now writes the findings and comprehension written in the reading process in order to discuss it with his colleagues. Topic 20. In O, diameter AB=6, BC is string, ∠ABC=30°, point P is on BC, point Q is on ⊙O, and OP⊥PQ.(1) is shown in Figure 1, when PQ∥AB, find The length of PQ; (2) As shown in Figure 2, when point P moves on BC, seek PQ