[mathematically]

Just a heads up, worksheet 5 has an error: (P ↔ Q) → (R ↔ S) → (P ∧ Q ↔ R ∧ S). That proposition is not actually true.

[BreakfastB0b]

It’s probably supposed to be (P & R) <-> (Q & S)

[mathematically]

Yup, transposition error.

[kevinbuzzard]

Thanks so much! Fixed.

[kevinbuzzard]

PS I cannot believe my undergraduate teaching material is on HN! I am a math lecturer and this is just my course notes for my UGs.

[mathematically]

It's very fun. Thanks for putting it together.