latex integral with circle code example

Example 1: integral latex

integral 
\[ \int_{a}^{b} x^2 \,dx \]

Example 2: latex number in circle

\documentclass{article}
\usepackage{tikz}
\newcommand*\circled[1]{\tikz[baseline=(char.base)]{
            \node[shape=circle,draw,inner sep=2pt] (char) {#1};}}
\begin{document}
Numbers aligned with the text:  \circled{1} \circled{2} \circled{3} end.
\end{document}