MathDB

2014.1

Part of Swiss NMO - geometry

Problems(1)

GH // t wanted, 4 concyclic points, tangent, reflection of AB wrt AC

Source: Switzerland - Swiss MO 2014 p1

7/16/2020
The points A,B,CA, B, C and DD lie in this order on the circle kk. Let tt be the tangent at kk through CC and ss the reflection of ABAB at ACAC. Let GG be the intersection of the straight line ACAC and BDBD and HH the intersection of the straight lines ss and CDCD. Show that GHGH is parallel to tt.
geometryreflectioncyclic quadrilateralparallel