\blue{1.\lim[\frac{1}{2}.\frac{3}{4}....\frac{2n-1}{2n}]\\ 2.\lim_{n \to \infty} [\frac{1}{\sqrt{n^2-1}}+\frac{1}{\sqrt{n^2-4}}+...+\frac{1}{\sqrt{n^2-(n-1)^2}}]