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self.play(Write(Tex(r'''$
        \Delta(W) = \left\{
            \begin{array}{ll}
                0 & \quad \text{if} \, s \notin W, t \notin W \\
                \Phi_{\text{tot}}(F) & \quad \text{if} \, s \in W, t \notin W \\
                -\Phi_{\text{tot}}(F) & \quad \text{if} \, s \notin W, t \in W \\
                0 & \quad \text{if} \, s \in W, t \in W
            \end{array}
        \right.
        $''')))