B.5.RR:1 - Problem frame

Use this pattern when reasoning that you could previously use needs to answer a changed question, or when a premise, observation or application condition changes. You need to know what still follows, what must be worked again and what can now be done.

The object of revision is the reasoning used for that question: its premises, intermediate contributions, conclusion and conditions of application. The relevant practice supplies its inference rules and the grounds for using its premises.

First useful move: state the change beside the result you now need. Find where the earlier reasoning used the changed condition, or where the new result requires a contribution the earlier argument did not supply.

This work requires enough subject knowledge to follow the argument. Use B.5.RA when that reasoning must first be recovered. If the established result already answers the new question under conditions that still hold, apply it and stop. Rebuilding the entire argument is useful when recovery would cost more, or when a separate obligation requires a full new derivation.