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This rule is used to join two formulas using an AND connective, or when used backwards to split an AND formula into its two subformulas
(to become separate goals).
To use it forwards:
- select both an empty line and And Introduction.
- then select, in the order you wish them to appear in the resulting formula, the two lines containing the formulas you require (Note
these lines must be in the scope of the empty line).
- the and formula will then be added to your proof.
To use it backwards:
- select both a goal line (this line must be an AND formula) and And Introduction.
- The two sub formulas will then appear as the conclusions in two new boxes (subproofs) in your proof.
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