digraph G {
       node [shape=circle];
       a_1 [texlbl="$x^2+\frac{\sin y}{y^2+\cos \beta}+\gamma_3$"];
       a_1 -> a_2 [label=" ", texlbl="$x_1+x_3^2+z+c+v~~$"];
       a_2 -> a_1;
}