2019浙教版九年级下册数学期末高效复习专题3圆的基本性质(解析版)精品教育.doc.pdf
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1、第 1 页期末高效复习专题 3圆的基本性质题型一点与圆的位置关系例 12019 大冶校级月考 若O 的半径为 5 cm,平面上有一点 A,OA6 cm,那么点 A 与O 的位置关系是(A)A点 A 在O 外B点 A 在O 上C点 A 在O 内D不能确定【解析】O 的半径为 5 cm,OA6 cm,dr,点 A 与O 的位置关系是点 A 在O 外变式跟进12019 宜昌在公园的 O 处附近有 E,F,G,H 四棵树,位置如图 1 所示(图中小正方形的边长均相等)现计划修建一座以O 为圆心,OA 为半径的圆形水池,要求池中不留树木,则E,F,G,H 四棵树中需要被移除的为(A)图 1 AE,F,G
2、BF,G,HCG,H,EDH,E,F【解析】OA1225,OE2OA,点 E 在O 内;OF2OA,点 F 在O 内;OG1OA,点 G 在O 内;OH22222 2OA,点 H 在O 外题型二垂径定理及其推论例 2如图 2,O 的直径 CD10,弦 AB8,ABCD,垂足为 M,则 DM的长为(D)A5 B6 C7 D8 图 2 例 2 答图【解析】连结 OA,如答图所示O 的直径 CD10,OA5,弦 AB8,ABCD,AM12AB1284,在 RtAOM 中,OMOA2AM2第 2 页52423,DMODOM538.【点悟】已知直径与弦垂直的问题中,常连半径构造直角三角形,其中斜边为圆的
3、半径,两直角边是弦长的一半和圆心到弦的距离,从而运用勾股定理来计算变式跟进2如图 3,AB 为O 的直径,弦 CDAB 于点 E,若 CD8,且 AEBE14,则 AB 的长度为(A)A10 B5 C12 D.53图 3 第 2 题答图【解析】如答图,连结 OC,设 AEx,AEBE14,BE4x,OC2.5x,OE1.5x,CDAB,CEDE12CD4,RtOCE 中,OE2CE2OC2,(1.5x)242(2.5x)2,x2,AB10.3有一座弧形的拱桥如图4,桥下水面的宽度AB 为 7.2 m,拱顶与水面的距离CD 的长为 2.4 m,现有一艘宽 3 m,船舱顶部为长方形并且高出水面2
4、m 的货船要经过这里,此货船能顺利通过这座拱桥吗?图 4 第 3 题答图解:如答图,连结 ON,OB.OCAB,D 为 AB 中点,AB7.2 m,BD12AB3.6 m.又CD2.4 m,设 OBOCONr,则 OD(r2.4)m.在 RtBOD 中,由勾股定理得r2(r2.4)23.62,解得 r3.9.CD2.4 m,船舱顶部为长方形并高出水面2 m,CE2.420.4(m),OErCE3.90.43.5(m),在 RtOEN 中,EN2ON2OE23.923.522.96(m2),EN1.72(m)MN2EN21.723.44 m3,此货船能顺利通过这座弧形拱桥题型三圆周角定理的综合文
5、档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9
6、F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H
7、5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10
8、T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I
9、5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:
10、CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P1
11、0G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO
12、10Y9F9P10G1第 3 页例 32019 市南区一模 如图 5,在直径为 AB 的O 中,C,D 是O 上的两点,AOD58,CDAB,则 ABC 的度数为 _61_图 5【解析】AOD58,ACDAOD29,CDAB,CABACD29,AB是直径,ACB90,ABC902961.【点悟】(1)在同圆(或等圆)中,圆心角(或圆周角)、弧、弦中只要有一组量相等,则其他对应的各组量也分别相等,利用这个性质可以将问题互相转化,达到求解或证明的目的;(2)注意圆中的隐含条件(半径相等)的应用;(3)圆周角定理及其推论,是进行圆内角度数转化与计算的主要依据,遇直径,要想到直径所对的圆周角是 90,
13、从而获得到直角三角形;遇到弧所对的圆周角与圆心角,要想到同弧所对的圆心角等于圆周角的2 倍以及同弧所对的圆周角相等变式跟进4如图 6,O 是正方形 ABCD 的外接圆,点 P 在O 上,则APB_45_图 6 第 4 题答图【解析】如答图,连结OA,OB.根据正方形的性质,得AOB90.再根据圆周角定理,得 APB45.52019 永嘉二模 如图 7,已知 AB 是半圆 O 的直径,OCAB 交半圆于点 C,D 是射线 OC 上一点,连结 AD 交半圆 O 于点 E,连结 BE,CE.(1)求证:EC 平分 BED;(2)当 EBED 时,求证:AECE.图 7 第 5 题答图证明:(1)AB
14、 是半圆 O 的直径,AEB90,DEB90.OCAB,AOCBOC90,BEC45,DEC45.BECDEC,即 EC 平分BED;(2)如答图,连结 BC,OE,在BEC与DEC 中,BEDE,BECDEC,ECEC,文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I
15、5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:
16、CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P1
17、0G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO
18、10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L1
19、0R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1
20、HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L
21、3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1第 4 页BECDEC,CBECDE.CDE90AABE,ABECBE.AOECOE,AECE.题型四弧长的计算例 4如图 8,ABC 是正三角形,曲线 CDEF 叫做“正三角形的渐开线”,其中,CD,DE,EF,圆心依次按 A,B,C循环,它们依次相连结若AB1,则曲线 CDEF 的长是 _4_(结果保留)图 8【解析】CD的长是120118023,
22、DE的长是120218043,EF的长是12031802,则曲线 CDEF 的长是234324.变式跟进6一个扇形的半径为8 cm,弧长为163 cm,则扇形的圆心角为 _120_【解析】设扇形的圆心角为n,根据题意得163n8180,解得 n120,扇形的圆心角为 120.题型五扇形的面积计算例 52019 河南如图 9,在扇形 AOB 中,AOB90,以点 A 为圆心,OA 的长为半径作 OC交AB于点 C,若 OA2,则阴影部分的面积是313图 9 例 5 答图【解析】如答图,连结 OC,AC,OAC 是等边三角形,扇形OBC 的圆心角是30,阴影部分的面积等于扇形OBC 的面积减去弓形
23、OC 的面积 S扇形OBC302236013,S弓形OC60223603422233,S阴影13233 313.【点悟】求不规则图形的面积,常转化为易解决的基本图形,然后求出各图形的面积,通过面积的和差求出结果变式跟进7 若扇形的半径为 3 cm,扇形的面积为 2 cm2,则该扇形的圆心角为 _80_,文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1
24、 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2
25、L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1文档编码:CP2L3F6I5G1 HJ10T9L10R2H5 ZO10Y9F9P10G1
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