theorem addSass (a b: nat): $ suc a + b = a + suc b $;
Step | Hyp | Ref | Expression |
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1 | eqtr4 | suc a + b = suc (a + b) -> a + suc b = suc (a + b) -> suc a + b = a + suc b |
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2 | addS1 | suc a + b = suc (a + b) |
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3 | 1, 2 | ax_mp | a + suc b = suc (a + b) -> suc a + b = a + suc b |
4 | addS2 | a + suc b = suc (a + b) |
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5 | 3, 4 | ax_mp | suc a + b = a + suc b |