AB//CD,OE平分∠BOC,OF⊥OE,OP⊥CD,∠ABO=40°,则下列结论:①∠BOE=70°②OF平分∠BO
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AB//CD,OE平分∠BOC,OF⊥OE,OP⊥CD,∠ABO=40°,则下列结论:①∠BOE=70°②OF平分∠BOD ③∠POE=∠BOE ④∠POB=2∠DOF,其中正确结论有( )理由
正确结论有(① ② ③)理由
①
∵ AB∥CD
∴ ∠ABO+∠BOC = 180
∠BOC = 180 -∠ABO = 180-40 = 140
∵ OE平分∠BOC
∴ ∠BOE = 1/2∠BOC = 70°
②
∵ AB∥CD
∴ ∠BOD = ∠ABO=40°
∴ ∠BOF=1/2∠BOD = 20
∵ OF⊥OE ∠BOE+∠BOF=90
∴ ∠BOF = 90 -∠BOE = 90-70 = 20 = 1/2∠BOD
OF平分∠BOD
③
∵ OP⊥CD
∴ ∠COE+POE = 90
∵ ∠COE = 1/2∠BOC = 70
∴ ∠POE = 90 -∠COE = 20
∵ ∠BOF = 1/2∠BOD = 20
∴ ∠POE=∠BOE
④ (不成立)
∵ ∠POB = ∠BOE -∠POE = 70 - 20 = 50
∴ ∠DOF = 1/2∠BOD = 20
∵ ∠POB ≠ 2∠DOF
①
∵ AB∥CD
∴ ∠ABO+∠BOC = 180
∠BOC = 180 -∠ABO = 180-40 = 140
∵ OE平分∠BOC
∴ ∠BOE = 1/2∠BOC = 70°
②
∵ AB∥CD
∴ ∠BOD = ∠ABO=40°
∴ ∠BOF=1/2∠BOD = 20
∵ OF⊥OE ∠BOE+∠BOF=90
∴ ∠BOF = 90 -∠BOE = 90-70 = 20 = 1/2∠BOD
OF平分∠BOD
③
∵ OP⊥CD
∴ ∠COE+POE = 90
∵ ∠COE = 1/2∠BOC = 70
∴ ∠POE = 90 -∠COE = 20
∵ ∠BOF = 1/2∠BOD = 20
∴ ∠POE=∠BOE
④ (不成立)
∵ ∠POB = ∠BOE -∠POE = 70 - 20 = 50
∴ ∠DOF = 1/2∠BOD = 20
∵ ∠POB ≠ 2∠DOF
AB//CD,OE平分∠BOC,OF⊥OE,OP⊥CD,∠ABO=40°,则下列结论:①∠BOE=70°②OF平分∠BO
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