cases' lr_exists with lr
case intro.intro.intro.intro.intro
LR : TNode
LCond RCond : Finset Formula
C : List SubPair
lr_exists : Nonempty (LocalRule (LCond, RCond) C)
preconL : LCond ⊆ LR.1
preconR : RCond ⊆ LR.2
⊢ Nonempty (LocalTableau LR)
case intro.intro.intro.intro.intro.intro
LR : TNode
LCond RCond : Finset Formula
C : List SubPair
preconL : LCond ⊆ LR.1
preconR : RCond ⊆ LR.2
lr : LocalRule (LCond, RCond) C
⊢ Nonempty (LocalTableau LR)