 Similarly, given a set of formulas in two variables \(\Delta(p, q)\) and an equation \(\delta \approx \varepsilon\), let \(\Delta(\delta , \varepsilon)\) denote the set of formulas obtained by replacing \(p\) by \(\delta\) and \(q\) by \(\varepsilon\) in all the formulas in \(\Delta\). Moreover, if \(\iEq\) is a set of equations, let