Τετάρτη 4 Μαΐου 2011

▪ India National Olympiad 2011

1. Let be points on the sides respectively of a triangle such that and Show that is equilateral.
2. Call a natural number faithful if there exist natural numbers such that and and
Show that all but a finite number of natural numbers are faithful.
Find the sum of all natural numbers which are not faithful.
3. Let and be two polynomials with integral coefficients such that is a prime and and Suppose that there exists a rational number such that Prove that
4. Suppose five of the nine vertices of a regular nine-sided polygon are arbitrarily chosen. Show that one can select four among these five such that they are the vertices of a trapezium.
5. Let be a cyclic quadrilateral inscribed in a circle Let be the midpoints of arcs of respectively. Suppose that Show that are all concurrent.
6. Find all functions satisfying

For all where  denotes the set of all real numbers.

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