\usepackage{gensymb} to your preamble, that should enable the command. Another alternative is the\textdegreecommand, which is provided by thetextcomppackage. And, finally,$^{\circ}$is another way of obtaining roughly the right symbol.
For example, in this case, to use the\iintsymbol you need to make sure you have\usepackage{amsmath}in your document preamble, i.e. before the\begin{document}statement. To see the packages Overleaf supports, readWhat packages do you support?
For example, in this case, to use the\iintsymbol you need to make sure you have\usepackage{amsmath}in your document preamble, i.e. before the\begin{document}statement. To see the packages Overleaf supports, readWhat packages do you support?
For example, in this case, to use the\iintsymbol you need to make sure you have\usepackage{amsmath}in your document preamble, i.e. before the\begin{document}statement. To see the packages Overleaf supports, readWhat packages do you support?
For example, in this case, to use the\iintsymbol you need to make sure you have\usepackage{amsmath}in your document preamble, i.e. before the\begin{document}statement. To see the packages Overleaf supports, readWhat packages do you support?