KwickClips Computer Systems · 42 sec · free
How many rows make p → q false?
Short answer. Only one: p true, q false.
What is p → q when p is false?
True.
p → q
| p q | p → q | Promise |
|---|---|---|
| T T | T | kept |
| T F | F | broken |
| F T | T | not broken |
| F F | T | not broken |
Remember
| p → q false only for T, F |
Score ninety, get a cycle. When is this promise false? Take each row in turn. Both true: kept. Ninety, no cycle: broken. The last two rows never break it, so true. One rule. False only when p is true and q is false.
This clip is from the full lesson: Propositional Logic: Propositions, Connectives and Valid Formulae — 8 minutes, with the tables, the quick answers and the whole lesson in text.
Useful for: ISC Class 11 Computer Science (868), ISC Class 12 Computer Science (868), ISC Class 12 Computer Science (868)
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Is p ∧ ~p a tautology?37 sec
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