Why is it not true that if $\Phi \vdash \exists x \phi$ then there is a term $t$ with $\Phi \vdash \phi \frac{t}{x}$?
102406
Why is it not true that if $\Phi \models \exists x \phi$ then there is a term $t$ with $\Phi \models \phi \frac{t}{x}$?
132532
Things around $(\forall x)(\Psi \Rightarrow \Phi) \Leftrightarrow ((\exists z)\Psi) \Rightarrow \Phi)$
109674
If $(I-T)^{-1}$ exists, can it always be written in a series representation?
52301
Omitting the hypotheses of finiteness of the measure in Egorov theorem
127000
When does $V = \ker(f) \oplus \operatorname{im}(f)$?
149907
$T\circ T=0:V\rightarrow V \implies R(T) \subset N(T)$
72906
Is $\frac{\partial}{\partial x_1}=\frac{\partial}{\partial y_1}$ if $x_1=y_1$?
142519
Uniqueness and Existence problem
146358
Why is there a $\frac 1 2$ in $\frac 1 2 mv^2$?
81873
Is $(X,\mathcal T)$ necessarily an indiscrete space?
116427
$(c^{\mu}\partial_{\mu}-m)\phi(x)=0$ not Lorentz-invariant?
65889
Showing $\Phi(x)=\int_0^x (x-t)f(t)\,dt$ is twice differentiable and finding $\Phi''(x)$
133405
$\lim_{x \rightarrow 0} f'(x) = L$ exists, does it follow that $f'(0)$ exists?
64941
Why is $1 - \frac{1}{1 - \frac{1}{1 - \ldots}}$ not real?
57055
Are $|X|$ and $\operatorname{sgn}(X)$ independent?
27782
Why does this proof of the chain rule not work?
130998
Is $\exists x \in A ~:~ P(x)$ the same as $\exists x ~:~ x \in A \implies P(x)$