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,圆周角,24.3,沪科,版 九,年级,第,24,章 圆,第,1,课时,圆周角定理及其推论,目标二,圆周角和弧的关系,C,C,1,2,3,4,5,答 案 呈 现,温馨,提示,:,点击,进入,讲评,习题链接,C,C,D,C,6,7,8,【,2021,常州】,如图,,BC,是,O,的直径,,AB,是,O,的弦,若,AOC,60,,则,OAB,的度数是,(,),A,20,B,25,C,30,D,35,1,C,【,2021,黄石】,如图,,A,,,B,是,O,上的两点,,AOB,60,,,OF,AB,交,O,于点,F,,则,BAF,等于,(,),A,20,B,22.5,C,15,D,12.5,C,2,【,2021,荆州】,如图,矩形,OABC,的边,OA,,,OC,分别在,x,轴、,y,轴的正半轴上,点,D,在,OA,的延长线上,若,A,(2,,,0),,,D,(4,,,0),,以,O,为圆心,,OD,长为半径的弧经过点,B,,交,y,轴正半轴于点,E,,连接,DE,,,BE,,,则,BED,的度数是,(,),A,15,B,22.5,C,30,D,45,C,3,【,2020,泸州】,如图,在,O,中,,AB,AC,,,ABC,70,,则,BOC,的度数为,(,),A,100,B,90,C,80,D,70,4,C,【,2021,白银】,如图,点,A,,,B,,,C,,,D,,,E,在,O,上,,AB,CD,,,AOB,42,,则,CED,(,),A,48,B,24,C,22,D,21,D,5,C,6,OAD,是等腰直角三角形,OAD,45.,OA,OB,,,OBA,OAD,45.,CAB,30,,,COB,2,CAB,60.,又,OB,OC,,,OBC,是等边三角形,OBC,60.,ABC,OBA,OBC,45,60,105.,如图,在,O,中,直径,CD,弦,AB,于点,E,,,AM,BC,于点,M,,交,CD,于点,N,,连接,AD,.,(1),求证:,AD,AN,;,7,证明:,ADC,与,ABC,都是,AC,所对的圆周角,,ADC,ABC,.,AE,CD,,,AM,BC,,,CEB,AMC,90.,ABC,C,CNM,C,.,ABC,CNM,.,又,CNM,AND,.,ABC,AND,.,ADC,AND,.,AD,AN,.,【教材,P,29,练习,T,3,变式】,【,2021,安徽】,如图,,O,中两条互相垂直的弦,AB,,,CD,交于点,E,.,(1),M,是,CD,的中点,,OM,3,,,CD,12,,求,O,的半径长;,8,(2),点,F,在,CD,上,且,CE,EF,,求证:,AF,BD,.,证明:如图,连接,AC,,延长,AF,交,BD,于点,G,.,AB,CD,,,CE,EF,,,AB,是,CF,的垂直平分线,AF,AC,,即,ACF,是等腰三角形,又,CE,EF,,,FAE,CAE,.,BC,BC,,,CAE,CDB,.,FAE,CDB,.,在,Rt,BDE,中,,CDB,B,90,,,FAE,B,90.,AGB,90.,AG,BD,,即,AF,BD,.,
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