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

State before:
S : Type
image_zero : S
image_succ : N → S → S
n m a b c : N
⊢ a + b + c = a + c + b
Tactic:
rw [add_assoc a b c]
State after:
S : Type
image_zero : S
image_succ : N → S → S
n m a b c : N
⊢ a + (b + c) = a + c + b

State before:
S : Type
image_zero : S
image_succ : N → S → S
n m a b c : N
⊢ a + (b + c) = a + c + b
Tactic:
rw [add_comm b c]
State after:
S : Type
image_zero : S
image_succ : N → S → S
n m a b c : N
⊢ a + (c + b) = a + c + b

State before:
S : Type
image_zero : S
image_succ : N → S → S
n m a b c : N
⊢ a + (c + b) = a + c + b
Tactic:
rw [← add_assoc]
State after:
no goals