\begin{graph}
    rankdir=LR
    node [shape=plaintext]
    v_1
    v_1 -> v_2 [label=\sqrt{2}+\frac{1}{(x+5)}, color=forestgreen]
    v_2 -> v_3 [label=$S \subseteq \{1,2,3\}^4$]
    v_3 -> v_1 [label=(f \circ g)^{-1}]
\end{graph}

%% note: the fields inside [] are comma-deliminted, so if there are commas inside a label= math expression, easylatex will break up the math expression at the comma; in this case you must put in the dollar signs manually