Time complexity of mutually recursive functions
If we set up recurrences, $T_1(n) = T_1(n-1) + T_2(n-1)$ and $T_2(n) = T_1(n-1) + T_2(n-1)$. So from there we can get that $T_1(n) = T_2(n)$, which implies that $T_1(n) = 2T_1(n-1)$. So for this, the two functions would be $O(2^n)$.