theorem nfmul {x: nat} (a b: nat x): $ FN/ x a $ > $ FN/ x b $ > $ FN/ x a * b $;
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | anl | y = a /\ z = b -> y = a |
|
2 | anr | y = a /\ z = b -> z = b |
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3 | 1, 2 | muleqd | y = a /\ z = b -> y * z = a * b |
4 | hyp h1 | FN/ x a |
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5 | hyp h2 | FN/ x b |
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6 | 3, 4, 5 | nfnlem2 | FN/ x a * b |