Looks like the sequence might be
[tex]a_{n+1}=\dfrac{a_n+\frac2{a_n}}2[/tex]
Assume that [tex]\displaystyle\lim_{n\to\infty}a_n=L[/tex]. Then taking the limit of both sides, we have
[tex]L=\dfrac{L+\frac2L}2\implies L=\pm\sqrt2[/tex]
But in order for the sequence to converge, only one of these values must be true. Since [tex]a(1)=2>0[/tex], each successive number will also be positive, so the limit must be [tex]L=\sqrt2[/tex].
