Logic / Unit 5 Logic 192 short lesson, about 20 seconds
Proof Notation
Captions available
The idea
Number every line. Justify every derived line by citing the lines used and the rule applied.
In practice
4. Q 1, 3, MP — line 4 is Q, obtained from lines 1 and 3 by modus ponens.
Where people slip
A line without a justification isn't a proof step; it's a wish.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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