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15 lines
497 B
15 lines
497 B
This sequent is provable.
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\setlength\subproofhorizspace{1.3em}
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\begin{logicproof}{2}
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\exists y \forall x P(x,y) & \prem \\
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\begin{subproof}
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\forall x P(x,y_0) & $\assum$ $\freshVar{$y_0$}$ \\
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\begin{subproof}
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P(x_0,y_0) & $\foralle 2$ $\freshVar{$x_0$}$ \\
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\exists y P(x_0,y) & $\existi 3$
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\end{subproof}
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\forall x \exists y P(x,y) & $\foralli3-4$
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\end{subproof}
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\forall x \exists y P(x,y) & $\existe 1,2-5$
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\end{logicproof}
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