Spermatogenesis is the biological process through which spermatozoa are produced from male primordial germ cells in the testes. This process involves mitotic and meiotic divisions, ultimately resulting in the formation of mature sperm cells capable of fertilizing an ovum.
Given, the function \( f(x) = \frac{a^x + a^{-x}}{2} \) (\( a > 2 \)), then \( f(x+y) + f(x-y) \) is equal to