> theorems like ∗22.92: α⊂β→α∪(β−α)
Either I misunderstand the notation or there seems to be something missing there - the right hand side of that implication arrow is not a formula.
I would assume that what is meant is α⊂β→α∪(β−α)=β
Either I misunderstand the notation or there seems to be something missing there - the right hand side of that implication arrow is not a formula.
I would assume that what is meant is α⊂β→α∪(β−α)=β