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Question Number 53031 by behi83417@gmail.com last updated on 16/Jan/19

Commented by behi83417@gmail.com last updated on 16/Jan/19

AB<CB.  ∡ABE=∡EBF=∡FBC  ......show that:    ((BE)/(BF)) >1  .

AB<CB.ABE=EBF=FBC......showthat:BEBF>1.

Answered by ajfour last updated on 16/Jan/19

let the three equal angles be θ.  ((BE)/(sin A)) = ((AB)/(sin ∠AEB))    &  ((BF)/(sin C)) =  ((BC)/(sin ∠CFB))   AB < BC   ⇒ ∠C < ∠A ⇒  sin C < sin A  further   ∠AEB+∠A+θ = ∠CFB+∠C+θ  ⇒ ∠CFB > ∠ AEB  from eqs. in first and second line  ((BE)/(BF)) = ((sin A)/(sin C))×((sin ∠CFB)/(sin ∠AEB))           = (>1)×(>1) > 1   hence  BE > BF .

letthethreeequalanglesbeθ.BEsinA=ABsinAEB&BFsinC=BCsinCFBAB<BCC<AsinC<sinAfurtherAEB+A+θ=CFB+C+θCFB>AEBfromeqs.infirstandsecondlineBEBF=sinAsinC×sinCFBsinAEB=(>1)×(>1)>1henceBE>BF.

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