The structure of the major product formed in the following reaction is:
The steam volatile compounds among the following are:
The structure of the major product formed in the following reaction is:
Given, the function \( f(x) = \frac{a^x + a^{-x}}{2} \) (\( a > 2 \)), then \( f(x+y) + f(x-y) \) is equal to