Geometry Problem. Post your solution in the comments box below.
Level: Mathematics Education, High School, Honors Geometry, College.
Click the figure below to enlarge the problem 939.
Tuesday, December 10, 2013
Geometry Problem 939: Circle, Tangent, Secant, Chord, Parallel, Midpoint
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<EDC=<ECA (tangent angle theorem) and <EDC=<EAF (parallel). That makes circumcircle of EAC tangent to FA and then by powerpoint theorem, FA^2=FE*FC. But FB^2=FE*FC, so FB^2=FA^2
ReplyDeleteConstruct circle circumscribe AEC
ReplyDeleteAngleBAE=angleEDC=angleECA
So AB is tangent to circle O and also to new constructed circle.
Further as FEC is the common chord of both circles it will bisect the tangent segment
QED
Triangles AEF,DEC & CAF are similar (Apply alternate segment theorem)
ReplyDeleteConsidering AEF & CAF
=> AF/FE = CF/FA
=> AF^2 = FC.FE = BF^2
FB is tangent to circle BCE
ReplyDeleteFA is tangent to circle ACE
Follows that AF = BF
Sumith Peiris
Moratuwa
Sri Lanka