Theorem: N.zero_add (LeanTeaching/TD/TD02.lean)

State before:
S : Type
image_zero : S
image_succ : N → S → S
n m a b c : N
⊢ 0 + a = a
Tactic:
induction a with
  | zero => rfl
| succ a hrec =>
  rw [add_succ, hrec]
State after:
no goals

State before:
case zero
S : Type
image_zero : S
image_succ : N → S → S
n m a b c : N
⊢ 0 + zero = zero
Tactic:
rfl
State after:
no goals

State before:
case succ
S : Type
image_zero : S
image_succ : N → S → S
n m a✝ b c a : N
hrec : 0 + a = a
⊢ 0 + succ a = succ a
Tactic:
rw [add_succ, hrec]
State after:
no goals