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import NNG.Levels.Multiplication.Level_2
Game "NNG"
World "Multiplication"
Level 3
Title "one_mul"
open MyNat
Introduction
"
These proofs from addition world might be useful here:
* `one_eq_succ_zero : 1 = succ 0`
* `succ_eq_add_one a : succ a = a + 1`
We just proved `mul_one`, now let's prove `one_mul`.
Then we will have proved, in fancy terms,
that 1 is a \"left and right identity\"
for multiplication (just like we showed that
0 is a left and right identity for addition
with `add_zero` and `zero_add`).
"
Statement MyNat.one_mul
"For any natural number $m$, we have $ 1 \\cdot m = m$."