Geometry Problem. Post your solution in the comments box below.
Level: Mathematics Education, High School, Honors Geometry, College.
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Thursday, December 19, 2013
Geometry Problem 947: Triangle, Circumcircle, Angle Bisector, Chord, Arc, Parallel
Labels:
angle bisector,
arc,
chord,
circumcircle,
parallel,
triangle
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Angle ABE = angle AFE = angle GBD
ReplyDeleteSo BDFG concylic
Angle FAC = angle FBG = angle FDG
QED
Let AF and BC intersect at P.
ReplyDeleteSince ABFC concyclic, (AD+DP)×FP = (CG+GP)×BP ... (1)
Since BDGF concyclic, DP×FP = GP×BP ... (2)
(1) - (2): AD×FP = CG×BP ... (3)
(2) / (3): DP/AD = GP/CG
Hence, DG//AC.
BDGFconcyclic=>< BFD= DG||AC (formeazacu secanta BC unghiuri corespondente congruente)
ReplyDeleteBFD=BGD,BFA=BCA, BGD=BCA,=> DG||AC
Delete