Handsomeja
幼苗
共回答了16个问题采纳率:100% 举报
(1)
![](https://img.yulucn.com/upload/b/c6/bc6571b914a49a899d390ee6c8aa28f7_thumb.jpg)
/秒;(2)①
![](https://img.yulucn.com/upload/9/61/96122e0b721568edc110f3d1fbff5e1f_thumb.jpg)
,
![](https://img.yulucn.com/upload/2/9a/29ac91c72b8d160b6b67201b63ca01a1_thumb.jpg)
或
![](https://img.yulucn.com/upload/6/60/660f3f0efe435961ff66c6e9f11b6d68_thumb.jpg)
;②
试题分析:(1)连接OQ,则OQ⊥PQ,OQ=1,OP=2,所以
![](https://img.yulucn.com/upload/0/4c/04c0f59c58d7e30e5843bbc3d1052408_thumb.jpg)
°,即
![](https://img.yulucn.com/upload/5/c9/5c9df81c0d6bec4ce96041293e0a3edd_thumb.jpg)
°,再根据弧长公式即可求得弧BQ的长,从而得到点Q的运动速度;
(2)①由(1)可知,当t=1时,△OPQ为直角三角形,所以,当Q'与Q关于x轴对称时,△OPQ'为直角三角形,此时
![](https://img.yulucn.com/upload/5/4e/54ebbf42c7c2779ea5e1e390c57a343a_thumb.jpg)
°,
![](https://img.yulucn.com/upload/0/49/049b3265664bde0862bcde99d57952f5_thumb.jpg)
,
![](https://img.yulucn.com/upload/9/61/96122e0b721568edc110f3d1fbff5e1f_thumb.jpg)
,再结合当Q'(0,-1)或Q'(0,1)时求解即可;
②当
![](https://img.yulucn.com/upload/2/9a/29ac91c72b8d160b6b67201b63ca01a1_thumb.jpg)
或
![](https://img.yulucn.com/upload/6/60/660f3f0efe435961ff66c6e9f11b6d68_thumb.jpg)
时,直线PQ与⊙O相交.作OM⊥PQ,根据等面积法及勾股定理可求得PM的长,从而求的结果.
(1)连接OQ,
则OQ⊥PQ,OQ=1,OP=2,所以
![](https://img.yulucn.com/upload/0/4c/04c0f59c58d7e30e5843bbc3d1052408_thumb.jpg)
°,即
![](https://img.yulucn.com/upload/5/c9/5c9df81c0d6bec4ce96041293e0a3edd_thumb.jpg)
°,
![](https://img.yulucn.com/upload/6/cd/6cd0cf1828eb0f4e977a1d607c2d2f27_thumb.jpg)
,所以点Q的运动速度为
![](https://img.yulucn.com/upload/b/c6/bc6571b914a49a899d390ee6c8aa28f7_thumb.jpg)
/秒;
(2)①由(1)可知,当t=1时,△OPQ为直角三角形,所以,当Q'与Q关于x轴对称时,△OPQ'为直角三角形,此时
![](https://img.yulucn.com/upload/5/4e/54ebbf42c7c2779ea5e1e390c57a343a_thumb.jpg)
°,
![](https://img.yulucn.com/upload/0/49/049b3265664bde0862bcde99d57952f5_thumb.jpg)
,
![](https://img.yulucn.com/upload/9/61/96122e0b721568edc110f3d1fbff5e1f_thumb.jpg)
,
当Q'(0,-1)或Q'(0,1)时,
![](https://img.yulucn.com/upload/d/64/d64446db9ade42de32b64fbf894e06c7_thumb.jpg)
°,此时
![](https://img.yulucn.com/upload/2/9a/29ac91c72b8d160b6b67201b63ca01a1_thumb.jpg)
或
![](https://img.yulucn.com/upload/6/60/660f3f0efe435961ff66c6e9f11b6d68_thumb.jpg)
,
即当
![](https://img.yulucn.com/upload/9/61/96122e0b721568edc110f3d1fbff5e1f_thumb.jpg)
,
![](https://img.yulucn.com/upload/2/9a/29ac91c72b8d160b6b67201b63ca01a1_thumb.jpg)
或
![](https://img.yulucn.com/upload/6/60/660f3f0efe435961ff66c6e9f11b6d68_thumb.jpg)
时,△OPQ是直角三角形;
②当
![](https://img.yulucn.com/upload/2/9a/29ac91c72b8d160b6b67201b63ca01a1_thumb.jpg)
或
![](https://img.yulucn.com/upload/6/60/660f3f0efe435961ff66c6e9f11b6d68_thumb.jpg)
时,直线PQ与⊙O相交.作OM⊥PQ,根据等面积法可知:
PQ×OM=OQ×OP,PQ=
![](https://img.yulucn.com/upload/d/10/d103c524ee3ae6d7034970921f9f0f54_thumb.jpg)
,
![](https://img.yulucn.com/upload/b/2d/b2df95b77611b85d849faba0f596b502_thumb.jpg)
,
![](https://img.yulucn.com/upload/a/04/a04b1b48d590581092c4153e8e269d6d_thumb.jpg)
,弦长
![](https://img.yulucn.com/upload/8/b8/8b8da9e49658de37b9be4c98e7b50ee4_thumb.jpg)
.
点评:动点的综合题是初中数学的重点和难点,在中考中极为常见,一般压轴题形式出现,难度较大.
1年前
2