Thursday, November 25, 2010

Problem 541: Right Triangle, Altitude, Angle Bisector, Congruence

Geometry Problem
Click the figure below to see the complete problem 541 about Right Triangle, Altitude, Angle Bisector, Congruence.

Problem 541. Right Triangle, Altitude, Angle Bisector, Congruence.
Go to Complete Problem 541

6 comments:

  1. draw EP perpendicular to AC
    ▲ADF ~ ▲AEP => AP/EP = AD/DF
    ▲ABE ~ ▲AEP => AB/BE = AP/EP
    AF bisector => AB/BF = AD/DF
    =>
    AB/BE = AB/BF
    =>
    BE = BF

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  2. Consider right triangles ABE, AFD
    Complements of the equal angles BAE,FAD are equal
    So Angle BEF = Angle AFD
    = Angle BFE (vertically opposite)
    etc

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  3. Triangle ABE ~ Triangle ADF by AA Test of similarity
    .....(angle FAD=angle BAF{given}, angle ABC=angle ADB=90{given})
    By c.a.s.t angle AFD=angle FEB
    angle AFD=angle BFE ....(vertically opposite angles)
    Hence, angle BFE=angle FEB.
    Therefore BF=BE....(Isosceles Angle Theorem)

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  4. The complements of both < BEA and AFD are A/2 and the result follows

    Sumith Peiris
    Moratuwa
    Sri Lanka

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  5. Problem 541
    Is<BEF=<ECA+<EAC=90-<BAE=90-<A/2, but <BFE=<AFD=90-<FAD=90-<A/2=
    Therefore BE=BF.
    APOSTOLIS MANOLOUDIS 4 HIGH SHCOOL OF KORYDALLOS PIRAEUS GREECE

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  6. Let <BAE=<EAC=x
    <ACB=90-2x
    <FBE=<DBC=2x
    <BEF=<BEA=90-x
    <BFE=<180-<FBE-<BEF=180-2x-(90-x)=90-x-<BEF
    Since <BEF=<BFE, BF=BE

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