Does direct proof cover all the cases in default?
113735
Do we need to prove that if x∉A in proposition "if A⊆B then A⋃B=B"?
46939
Natural deduction, Proof $\vdash$ $P\Rightarrow(Q\Rightarrow P)$
131496
What exactly does GenerateConditions do?
66366
How to change the word "Proof" in the proof environment?
6535
Proof of for-all / there-exists "negation"?
93410
How to prove ~ (~P & ~Q) : P ∨ Q by natural deduction
104871
Direct cut-elimination for natural deduction.
149947
hide proof environment for restructuring
8342
Is short-circuiting logical operators mandated? And evaluation order?
142534
Proof of $k {n\choose k} = n {n-1 \choose k-1}$ using direct proof
147874
Why does the existence of independent statements not prove consistency?
112539
Can I disprove a claim using the contrapositive?
9282
Prove using natural deduction $((P \land Q) \rightarrow R) \vdash (P \rightarrow R) \lor (Q\rightarrow R)$
49994
Deduction of $\forall y \exists x (x=y)$
41604
default value for the 2nd argument in Power for pattern matching
148239
natural deduction proof with De Morgan's laws
27356
Lower bound on proof length