Logic Lab

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Typing symbols

¬: ~ !
∧: & ^
∨: | v
→: -> => ⊃
↔: <-> <=> ≡
↑ ↓: NAND, NOR (keypad)
⊤ ⊥: always true / always false

Type the whole formula, then press Enter (or click Build). The builder only checks whether it’s a wff at that point.

Sentence letters are single capitals like A, B, C (A1, P2 also work), so AB is two letters, not one. As in the textbook, ¬ applies to what immediately follows it and outer parentheses can be dropped. Mixing binary connectives without parentheses, as in A ∧ B ∨ C, is ambiguous, so the builder asks you to add them. Chains of a single ∧ or ∨ (A ∧ B ∧ C) are fine.

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