第10章 相交线、平行线与平移,10.1 相交线,解:( 1 )AOD的对顶角是BOC,EOC的对顶角是DOF. ( 2 )BOD=50. ( 3 )因为BOE=EOD+BOD,EOD=COF, 所以BOE=BOD+COF=140.,解:延长AO,BO分别至点C,点D,测量COD的度数即可. 理由:对顶角相等.,解:( 1 )AOC,BOD,EOD. ( 2 )由( 1 )知DOE=BOD=180-AOD=38,AOE=AOD-DOE=104.,解:( 1 )AOE=30. ( 2 )OB是DOF的平分线. 理由:AOE=30,BOE=180-AOE=150, OF平分BOE,BOF=75, 又BOD=75,BOD=BOF, OB是DOF的平分线.,解:( 1 )OE平分BOD,BOE=40, BOD=80,BOC=100. OF平分AOB,AOF=BOF=90, COF=100-90=10. ( 2 )COF=180-2x-90=90-2x.,解:( 4 )n( n-1 ). ( 5 )20182019=4074342.,
