[Brownian]

จงพิสูจน์ว่า. $$\cos (2558 \arctan 2 )=\frac{1- (\matrix{2558 \\ 2})2^2+(\matrix{2558 \\ 4})2^4-(\matrix{2558 \\ 6})2^6+...-2^{2558}}{5^{1279}} $$