Exercise · ZW-FORMAL-PROOF-007 · ★★☆ Intermediate
The first step of a proof can be...
Choose one option.
Show answer
- B. An allowed hypothesis
Explanation
The first step has no earlier lines, so it can only be an axiom or an allowed hypothesis. A conclusion without a reason is not valid as a first step.
Review the concept: Formal proof
A formal proof of \(\varphi_n\) is a sequence \(\varphi_1,\ldots,\varphi_n\) in which each term is an axiom, an admitted hypothesis, or the result of a rule applied to earlier terms.
\[\varphi_1,\varphi_2,\ldots,\varphi_n\vdash\varphi_n\]
More practice problems: formal proof
- ZW-FORMAL-PROOF-001 A formal proof is a...
- ZW-FORMAL-PROOF-002 Each line of a formal proof must be...
- ZW-FORMAL-PROOF-003 The last line of a proof is usually...
- ZW-FORMAL-PROOF-004 A formal proof depends on...
- ZW-FORMAL-PROOF-005 Which step does not belong to a formal proof?
- ZW-FORMAL-PROOF-006 A formal proof is a sequence of...
- ZW-FORMAL-PROOF-008 A line of a proof must be justifiable by...
- ZW-FORMAL-PROOF-009 A formal proof has the lines P→ Q and P, both allowed hypotheses. Which line can legitimately be ad…