OMCC 2003

Two players $A$ and $B$ take turns playing the following game: There is a pile of $2003$ stones. In his first turn, $A$ selects a divisor of $2003$ and removes this number of stones from the pile. $B$ then chooses a divisor of the number of remaining stones, and removes that number of stones from the new pile, and so on. The player who has to remove the last stone loses. Show that one of the two players has a winning strategy and describe the strategy.

$S$ is a circle with $AB$ a diameter and $t$ is the tangent line to $S$ at $B$ . Consider the two points $C$ and $D$ on $t$ such that $B$ is between $C$ and $D$ . Suppose $E$ and $F$ are the intersections of $S$ with $AC$ and $AD$ and $G$ and $H$ are the intersections of $S$ with $CF$ and $DE$ . Show that $AH=AG$ .

Let $a$ and $b$ be positive integers with $a>1$ and $b>2$ . Prove that $a^b+1\ge b(a+1)$ and determine when there is inequality.

$S_1$ and $S_2$ are two circles that intersect at two different points $P$ and $Q$ . Let $\ell_1$ and $\ell_2$ be two parallel lines such that $\ell_1$ passes through the point $P$ and intersects $S_1,S_2$ at $A_1,A_2$ respectively (both distinct from $P$ ), and $\ell_2$ passes through the point $Q$ and intersects $S_1,S_2$ at $B_1,B_2$ respectively (both distinct from $Q$ ). Show that the triangles $A_1QA_2$ and $B_1PB_2$ have the same perimeter.

A square board with $8\text{cm}$ sides is divided into $64$ squares square with each side $1\text{cm}$ . Each box can be painted white or black. Find the total number of ways to colour the board so that each square of side $2\text{cm}$ formed by four squares with a common vertex contains two white and two black squares.