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阶段方法技巧训练(二),专训,2,与相交线、平行线相,关的四类角的计算,习题课,与相交线、平行线有关的角的计算大致有两类,呈现形式,一类是利用余角、补角、对顶角、角平,分线等进行相关的计算,另一类是利用平行线的性,质和判定进行,有,关的计算,1,类型,利用平角、对顶角转换求角,1,如图,已知直线,AB,,,CD,相交于点,O,,,OA,平分,EOC,,,若,EOC,EOD,23,,求,BOD,的度数,解:由,EOC,EOD,23,,,设,EOC,2,x,,则,EOD,3,x,.,因为,EOC,_,180(,_,),,,所以,2,x,3,x,180,,解得,x,36.,所以,EOC,72.,因为,OA,平分,EOC,(已知),,所以,AOC,EOC,36.,因为,BOD,AOC,(,),,所以,BOD,EOD,平角的定义,对顶角相等,36,2,利用垂线求角,类型,2,如图,已知,FE,AB,于点,E,,,CD,是过点,E,的直线,,且,AEC,120,,则,DEF,.,30,3,如图,,MO,NO,于点,O,,,OG,平分,MOP,,,PON,3,MOG,,则,GOP,的度数为,.,54,设,GOP,x,,则,MOG,x,,,PON,3,x,,由题意得,x,x,3,x,360,90,,解得,x,54.,GOP,54.,4,如图,两直线,AB,,,CD,相交于点,O,,,OE,平分,BOD,,,AOC,AOD,711.,(,1,)求,COE,的度数;,(,2,)若,OF,OE,,求,COF,的度数,(1),AOC,AOD,711,,,AOC,AOD,180,,,AOC,70,,,AOD,110.,又,OE,平分,BOD,,,DOE,DOB,AOC,70,35.,COE,180,DOE,180,35,145.,(2),OF,OE,,,FOE,90.,又,DOE,35,,,FOD,90,DOE,90,35,55.,COF,180,FOD,180,55,125.,解:,3,直接利用平行线的性质求角,类型,5,如图,已知,AB,CD,,,AMP,150,,,PND,60.,试说明:,MP,PN,.,如图,过点,P,作,PE,AB,.,PE,AB,,,AMP,MPE,180.,MPE,180,AMP,180,150,30.,AB,CD,,,PE,AB,,,PE,CD,,,EPN,PND,60.,MPN,MPE,EPN,30,60,90,,,即,MP,PN,.,解:,4,综合应用平行线的性质与判定求角,类型,6,如图,,1,与,2,互补,,3,135,,则,4,的度数,是(),A,45 B,55 C,65 D,75,A,1,72,,,2,72,,,1,2.,a,b,.,3,4,180.,又,3,60,,,4,120.,7,如图,,1,72,,,2,72,,,3,60,,求,4,的度数,解:,
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