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36th Austrian Mathematical Olympiad 2005

Source: round 1, problem 2

February 11, 2009
geometry unsolvedgeometry

Problem Statement

Construct the semicircle h h with the diameter AB AB and the midpoint M M. Now construct the semicircle k k with the diameter MB MB on the same side as h h. Let X X and Y Y be points on k k, such that the arc BX BX is 32 \frac{3}{2} times the arc BY BY. The line MY MY intersects the line BX BX in D D and the semicircle h h in C C. Show that Y Y ist he midpoint of CD CD.