In this question you have to show that the validity of a sequent cannot be proved by finding a model where all formulas to the left of evaluate to T but the formula to the right of evaluates to .
Question 8.1
Show that the validity of the following sequent
∀x((x)→(x)) 卜 ∀x((x) ∨ (x))|
cannot be proved by finding a mathematical model where the formula to the left of 卜-evaluates to T but the formula to the right of -evaluates to .