Proving $\vdash (\exists x)(A\rightarrow(\forall x)A)$
5701
Quantifier difference notation
116768
Problem 5, sec. 13 in Munkres' Topology, 2nd ed.: How to prove the assertion if $\mathscr{A}$ is a subbasis?
1027
Why is this true? $(\exists x)(P(x) \Rightarrow (\forall y) P(y))$
20581
How to show that $\Gamma\vdash (\varphi\to\neg\varphi)\to\varphi$?
93707
Formal proof for $q \land \neg q \vdash r \land \neg r$
137990
Justify each step in the following proof of Proposition 3.9 (a). I like to know if I'm in the right track and I'm also missing a few of them
131257
$\to$ vs. $\vdash$ in logic
39708
Proving $(A\le B)\vee (B\le A)$ for sets $A$ and $B$
149801
prove that $TS = ST$
73074
$f \text{ convex }\Rightarrow \forall (x_0,f(x_0))\in \Gamma(f) \exists a : \forall x\in \mathbb{R}, f(x) \ge a(x-x_0)+f(x_0)$
1371
Prove that $f'(a)=\lim_{x\rightarrow a}f'(x)$.
46939
Natural deduction, Proof $\vdash$ $P\Rightarrow(Q\Rightarrow P)$
61640
Prove c exists for f:[0,1] -> R
93771
Prove that for any set $A$ there is some $x \notin A$
76110
Proving that the zero vector is unique
6169
If $ A^3=A$ prove that $Ker\left(A-I\right)+Im\left(A-I\right)=V$
150720
Given that $W$ is a subspace of $V$, prove: $\dim W=\dim V \implies W=V$