2023-2 Modal Logic (Segment 2) Q) UG, MP. E! is primitive, ∼ , ∨ are primitive and we have the usual definitions. Sketch proofs of: ① ├FL (∀x)( E!x ≡ (∃y)(x = y)). ② ├FL (∀y) ((∀x) ϕx ⊃ ϕy). Now consider the system FL* which is just like the above except that (∀y) ((∀x) ϕx ⊃ ϕy) replaces axiom schemas 2 and 3, and E! is dropped as a primitive sign. Sketch proofs of: ③ ├FL* (∀x) (∃y)(x = y) ④ ├FL..