4th Eötvös Competition 1897

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1.  ABC is a right-angled triangle. Show that sin A sin B sin(A - B) + sin B sin C sin(B - C) + sin C sin A sin(C - A) + sin(A - B) sin(B - C) sin(C - A) = 0.
2.  ABC is an arbitrary triangle. Show that sin(A/2) sin(B/2) sin(C/2) < 1/4.
3.  The line L contains the distinct points A, B, C, D in that order. Construct a rectangle whose sides (or their extensions) intersect L at A, B, C, D and such that the side which intersects L at C has length k. How many such rectangles are there?

 

The original problems are in Hungarian. They are available on the KöMaL archive on the web. They are also available in English (with solutions in): (Translated by Elvira Rapaport) József Kürschák, G Hajós, G Neukomm & J Surányi, Hungarian Problem Book 1, 1894-1905, MAA 1963. Out of print, but available in some university libraries.

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John Scholes
jscholes@kalva.demon.co.uk
20 Oct 1999