Challenging Geometry Puzzle: Problem 1562. Share your solution by posting it in the comment box provided.
Audience: Mathematics Education - K-12 Schools, Honors Geometry, and College Level.
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Let EF intersects BD at N
ReplyDelete<EHF=<EBF=90° thus B, E, H, F concyclic
<BEF=<BHF=45°=<EBD hence NE=NB.
Similarly NB=NF so NE=NF therefore N is the midpoint EF
<BDC=<A+<B/2=45°+<A = <BEH thus B, E, D, F concyclic
<EDF=<EHF=90° and DN median so DN=EF/2=BN
Therefore N is the midpoint BD
Let EF, BD cut at K
ReplyDelete< EBD = 45 = < EHD, hence B,E,D,H,F is concyclic and < BDE = < BHE = 45 = < DBE
It follows that the 6 triangles BDK, BFK, BEF, DKE, DKF, DEF are all right isosceles and so BEDF is a square and BK = KD
But BM = MD so M and K coincide
Therefore E,M,F are collinear
Sumith Peiris
Moratuwa
Sri Lanka