Geometry Problem
Click the figure below to see the complete problem 541 about Right Triangle, Altitude, Angle Bisector, Congruence.
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Thursday, November 25, 2010
Problem 541: Right Triangle, Altitude, Angle Bisector, Congruence
Labels:
altitude,
angle bisector,
congruence,
right triangle
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draw EP perpendicular to AC
ReplyDelete▲ADF ~ ▲AEP => AP/EP = AD/DF
▲ABE ~ ▲AEP => AB/BE = AP/EP
AF bisector => AB/BF = AD/DF
=>
AB/BE = AB/BF
=>
BE = BF
Consider right triangles ABE, AFD
ReplyDeleteComplements of the equal angles BAE,FAD are equal
So Angle BEF = Angle AFD
= Angle BFE (vertically opposite)
etc
Triangle ABE ~ Triangle ADF by AA Test of similarity
ReplyDelete.....(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)
The complements of both < BEA and AFD are A/2 and the result follows
ReplyDeleteSumith Peiris
Moratuwa
Sri Lanka
Problem 541
ReplyDeleteIs<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
Let <BAE=<EAC=x
ReplyDelete<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