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Forum URL: http://www.cut-the-knot.org/cgi-bin/dcforum/forumctk.cgi
Forum Name: College math
Topic ID: 688
Message ID: 0
#0, Two Equilateral Triangles - Seven Concyclic Points
Posted by Bui Quang Tuan on Aug-14-08 at 09:23 AM
Dear All My Friends,
Point B is on segment AC. Construct two equilaterals triangles XAB, YBC on one side of segment AC. Please prove following seven points are concyclic:
- Point B
- Intersection of XC, YA
- Midpoints of AC, XC, YA, XB, YB

Best regards,
Bui Quang Tuan