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MathNet 2009-part-05 — 172 problems (EN–VI) Question 65

Math Olympiad Vault · MathNet 2009-part-05 — 172 problems (EN–VI)

Question 65

The vertices of a regular hexagon are labeled $\cos (\theta)$, $\cos (2 \theta)$, $\cos (3 \theta)$, $\cos (4 \theta)$, $\cos (5 \theta)$, $\cos (6 \theta)$. For every pair of vertices, Bob draws a blue line through the vertices if one of these functions can be expressed as a polynomial function of the other (that holds for all real $\theta$), and otherwise Roberta draws a red line through the vertices. In the resulting graph, how many triangles whose vertices lie on the hexagon have at least one red and at least one blue edge?