(a) If $\left\{a_n\right\}$ is convergent, show that
$$
\lim _{n \rightarrow \infty} a_{n+1}=\lim _{n \rightarrow \infty} a_n
$$
(b) A sequence $\left\{a_n\right\}$ is defined by $a_1=1$ and $a_{n+1}=1 /\left(1+a_n\right)$ for $n \geqslant 1$. Assuming that $\left\{a_n\right\}$ is convergent, find its limit.