Show that the following is a tautology, without using truth tables: $[(p\to q)\wedge(q\to r)]\to(p\to r)$
52585
How to prove that $[(p \to q) \land (q \to r)] \to (p \to r)$ is a tautology without using the truth table?
12569
Using the terms 'theorem 'and 'tautology'
87257
How to prove this sequent using natural deduction?
109858
How could a statement be true without proof?
38785
Prove previsibility and $E[X_{T \wedge n}] \le E[X_{S \wedge n}]$
108955
Showing $(\mathbb{Q},+)$ is not isomorphic to $(\mathbb{R},+)$
48614
Why is "$P \Rightarrow Q$" equivalent to "$\neg Q \Rightarrow \neg P$"?
139064
Show by using logical connectives laws that $(P\to Q) \land (Q \to R) $ is equivalent to $(P \to R) \land [(P \iff Q) \lor (R \iff Q)]$
41223
How to check, whether the formula is a tautology
15504
In classical logic, why is $(p\Rightarrow q)$ True if $p$ is False and $q$ is True?
92492
Natural Deduction: $(p \lor q)\to r\vdash p \to r$ and $p\to\neg q\leftrightarrow(r\lor s),\neg s\vdash (p\land \neg q)\to r$
21035
Clarifying on how if p,q is logically equivalent to p only if q
70117
Show that $(p \to q) \lor (q \to p)$ is a tautology
109685
An invalid argument, the conclusion of which is a tautology
147375
Prove :(P → Q) ∨ (Q → P) using natural deduction
45323
How to prove $\vdash\neg P\to (P\to Q)$?
143999
Prove that formula is not tautology.