MathDB
Geometry problem

Source: Polish National Olympiad 2015 2nd round, 6th problem

March 3, 2015
geometrycircumcircle

Problem Statement

Let ABCABC be a triangle. Let KK be a midpoint of BCBC and MM be a point on the segment ABAB. L=KMACL=KM \cap AC and CC lies on the segment ACAC between AA and LL. Let NN be a midpoint of MLML. ANAN cuts circumcircle of ΔABC\Delta ABC in SS and SNS \neq N. Prove that circumcircle of ΔKSN\Delta KSN is tangent to BCBC.