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MathNet 2014 Question 4

Math Olympiad Vault · MathNet 2014

Question 4

Let $ABC$ be a non-isosceles triangle inscribed in a circle $\Gamma$ of radius $R$. The circle through $A$ tangent to $BC$ at $C$ meets again at $D$ the circle through $B$ tangent to $AC$ at $C$.

a) Prove that $CD\leq R$.

b) Prove that as $C$ moves on $\Gamma$, the line $CD$ passes through a fixed point.