| A1. Given θ in the range (0, π) how many (incongruent) triangles ABC have angle A = θ, BC = 1, and the following four points concyclic: A, the centroid, the midpoint of AB and the midpoint of AC? |
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| A2. x1, ... , xn are positive reals. sk is the sum of all products of k of the xi (for example, if n = 3, s1 = x1 + x2 + x3, s2 = x1x2 + x2x3 + x3x1, s3 = x1x2x3). Show that sksn-k ≥ (nCk)2 sn for 0 < k < n. |
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| A3. A triangle ABC has base AB = 1 and the altitude from C length h. What is the maximum possible product of the three altitudes? For which triangles is it achieved? |
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| A4. A graph with n > 1 points satisfies the following conditions: (1) no point has edges to all the other points, (2) there are no triangles, (3) given any two points A, B such that there is no edge AB, there is exactly one point C such that there are edges AC and BC. Prove that each point has the same number of edges. Find the smallest possible n. |
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| A5. Show that for any n ≥ 6 we can find a convex hexagon which can be divided into n congruent triangles. |
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To avoid possible copyright problems, I have changed the wording, but not the substance, of the problems.
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© John Scholes
jscholes@kalva.demon.co.uk
5 April 2002