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2011 xIMC keystage2-EMIC team Question 3

xIMC · 2011 xIMC keystage2-EMIC team

Question 3

A light beam reflects around a circle: at each boundary point its angles with the radius before and after reflection are equal. Starting at $A_0$, it hits $A_1,A_2,\ldots$. Point $A_{95}$ first coincides with $A_0$. How many choices of $A_1$ are possible?