Question 165
Let $x$ and $y$ be real numbers satisfying $x - y + 1 \neq 0$. If
$$
1 + \cos^2(2007x + 2008y - 1) = \frac{x^2 + y^2 + 2(1+x)(1-y)}{x - y + 1},
$$
find the minimum value of $xy$.
$$
1 + \cos^2(2007x + 2008y - 1) = \frac{x^2 + y^2 + 2(1+x)(1-y)}{x - y + 1},
$$
find the minimum value of $xy$.