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123 | 123 | Now for the inductive step. We prove the case for $n+1$, assuming the |
124 | 124 | case for~$n$. So suppose $a < \num {n+2}$. Again using $!Q_3$ we can |
125 | 125 | distinguish two cases: $\eq[a][\Obj 0]$ and for some $b$, |
126 | | -$\eq[a][c']$. In the first case, $\eq[a][\Obj 0] \lor \dots \lor |
127 | | -\eq[a][\num{n+1}]$ follows trivially. In the second case, we have $c' |
128 | | -< \num {n+2}$, i.e., $c' < \num{n+1}'$. By axiom~$!Q_8$, for some $d$, |
129 | | -$\eq[(d'+c')][\num{n+1}']$. By axiom $!Q_5$, |
130 | | -$\eq[(d'+c)'][\num{n+1}']$. By axiom~$!Q_1$, $\eq[(d'+c)][\num{n+1}]$, |
131 | | -and so $c < \num{n+1}$ by axiom~$!Q_8$. By inductive hypothesis, |
132 | | -$\eq[c][\Obj 0] \lor \dots \lor \eq[c][\num{n}]$. From this, we get |
133 | | -$\eq[c'][\Obj 0'] \lor \dots \lor \eq[c'][\num{n}']$ by logic, and so |
| 126 | +$\eq[a][b']$. In the first case, $\eq[a][\Obj 0] \lor \dots \lor |
| 127 | +\eq[a][\num{n+1}]$ follows trivially. In the second case, we have $b' |
| 128 | +< \num {n+2}$, i.e., $b' < \num{n+1}'$. By axiom~$!Q_8$, for some $c$, |
| 129 | +$\eq[(c'+b')][\num{n+1}']$. By axiom $!Q_5$, |
| 130 | +$\eq[(c'+b)'][\num{n+1}']$. By axiom~$!Q_1$, $\eq[(c'+b)][\num{n+1}]$, |
| 131 | +and so $b < \num{n+1}$ by axiom~$!Q_8$. By inductive hypothesis, |
| 132 | +$\eq[b][\Obj 0] \lor \dots \lor \eq[b][\num{n}]$. From this, we get |
| 133 | +$\eq[b'][\Obj 0'] \lor \dots \lor \eq[b'][\num{n}']$ by logic, and so |
134 | 134 | $\eq[a][\num{1}] \lor \dots \lor \eq[a][\num{n+1}]$ since |
135 | | -$\eq[a][c']$. |
| 135 | +$\eq[a][b']$. |
136 | 136 | \end{proof} |
137 | 137 |
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138 | 138 | \begin{lem} |
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