Theorem: rot_zero_vadd (Instructor/Lectures/grad/case_study_symmetries_key.lean)

State before:
⊢ ∀ (p : State), 0 +ᵥ p = p
Tactic:
intro p
State after:
p : State
⊢ 0 +ᵥ p = p

State before:
p : State
⊢ 0 +ᵥ p = p
Tactic:
cases p
State after:
case s0

⊢ 0 +ᵥ s0 = s0

case s120

⊢ 0 +ᵥ s120 = s120

case s240

⊢ 0 +ᵥ s240 = s240

State before:
case s0

⊢ 0 +ᵥ s0 = s0

case s120

⊢ 0 +ᵥ s120 = s120

case s240

⊢ 0 +ᵥ s240 = s240
Tactic:
repeat { rfl }
State after:
no goals

State before:
case s240

⊢ 0 +ᵥ s240 = s240
Tactic:
rfl
State after:
no goals