Τετάρτη 4 Μαΐου 2011

▪ Kyrgyzstan National Olympiad 2011

1. For a given chord of a circle discussed the triangle , whose base is the diameter of this circle,which do not intersect the , and the sides and pass through the ends of and of the chord . Prove that the heights of all such triangles drawn from the vertex to the side , intersect at one point.
2. In a convex -gon all angles are equal from a certain point, located inside the -gon, all its sides are seen under equal angles. Can we conclude that this -gon is regular?
3. Given positive numbers with . Prove that .
4. Given equation , with real . Prove that .
5. Points and are chosen on sides and ,respectively, in a triangle , such that point is interserction of lines and . Given that . Prove that .
6. a) Among the pairwise distances between the points of the plane, prove that one and the same number occurs not more than times.
b) Find a maximum number of times may meet the same number among the pairwise distances between points of the plane.

7. Given that and , for natural . Prove that .
8. Given a sequence of real numbers with , where . What must be value of , so that and becomes equal?

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