Question

Why must $x$ be not free in $\psi$ in order for $(\psi\to\phi)\vDash[\psi\to(\forall x\phi)]$?

score 278 · Answer 1 · 2026-03-25 14:40:13

278

Views

Why must $x$ be not free in $\psi$ in order for $(\psi\to\phi)\vDash[\psi\to(\forall x\phi)]$?

Published on 25 Mar 2026 - 14:40

score 123 · Answer 2 · 2018-06-19 11:11:43

123

Views

Where is the mistake in the proof that $\lim_{x\to \infty } \left(\frac{1}{\ln (x)}\right) = 1$?

Published on 19 Jun 2018 - 11:11

score 613 · Answer 3 · 2026-03-27 13:25:27

613

Views

Sum of the square of natural numbers - Mathematical Proof

Published on 27 Mar 2026 - 13:25

score 77 · Answer 4 · 2026-03-25 18:31:25

77

Views

$f$ is $1-1$ iff $f(A)\cap f(B)\subset f(A\cap B)$

Published on 25 Mar 2026 - 18:31

score 50 · Answer 5 · 2018-06-19 13:58:22

50

Views

Solving $y'''-y=\frac{1}{3}\left(e^x+e^{wx}+e^{w^2x}\right)$ by power series

Published on 19 Jun 2018 - 13:58

score 39 · Answer 6 · 2018-06-19 15:48:39

39

Views

Help with if $m \equiv 2 \operatorname{mod} 4$, then $\nexists x,y \in N : x^2 - y^2 = m$ proof.

Published on 19 Jun 2018 - 15:48

score 315 · Answer 7 · 2026-03-28 18:12:48

315

Views

Example for why K being compact needed.

Published on 28 Mar 2026 - 18:12

score 424 · Answer 8 · 2018-06-19 19:33:07

424

Views

Show that if the restriction f : [0, ∞) → R of f to the interval [0, ∞) is strictly decreasing, then f : R → R is strictly decreasing

Published on 19 Jun 2018 - 19:33

score 1.4k · Answer 9 · 2026-03-26 04:35:13

1.4k

Views

If $f \in R(\alpha)$ and if $\int_a ^b f~ d \alpha = 0$ then, prove that $\alpha$ must be constant

Published on 26 Mar 2026 - 4:35

score 406 · Answer 10 · 2026-03-26 01:01:39

406

Views

Clarification needed with Rudin Theorem 1.11

Published on 26 Mar 2026 - 1:01

score 124 · Answer 11 · 2026-03-25 13:54:50

124

Views

$\lim_{n\to\infty}a = \lim_{n\to\infty}b$ implies $a=b$

Published on 25 Mar 2026 - 13:54

score 311 · Answer 12 · 2026-03-25 13:53:33

311

Views

Mulitplication of Cauchy sequences is well defined

Published on 25 Mar 2026 - 13:53

score 41 · Answer 13 · 2026-03-25 07:39:55

41

Views

Computation Verification (Kähler Geometry)

Published on 25 Mar 2026 - 7:39

score 101 · Answer 14 · 2026-03-26 15:51:40

101

Views

Tautology question

Published on 26 Mar 2026 - 15:51

score 68 · Answer 15 · 2018-06-20 02:38:04

68

Views

Proof Verification For A Proof That The Domain Of An Inverse Function = Range Of Original Function

Published on 20 Jun 2018 - 2:38

List Question

Why must $x$ be not free in $\psi$ in order for $(\psi\to\phi)\vDash[\psi\to(\forall x\phi)]$?

Where is the mistake in the proof that $\lim_{x\to \infty } \left(\frac{1}{\ln (x)}\right) = 1$?

Sum of the square of natural numbers - Mathematical Proof

$f$ is $1-1$ iff $f(A)\cap f(B)\subset f(A\cap B)$

Solving $y'''-y=\frac{1}{3}\left(e^x+e^{wx}+e^{w^2x}\right)$ by power series

Help with if $m \equiv 2 \operatorname{mod} 4$, then $\nexists x,y \in N : x^2 - y^2 = m$ proof.

Example for why K being compact needed.

Show that if the restriction f : [0, ∞) → R of f to the interval [0, ∞) is strictly decreasing, then f : R → R is strictly decreasing

If $f \in R(\alpha)$ and if $\int_a ^b f~ d \alpha = 0$ then, prove that $\alpha$ must be constant

Clarification needed with Rudin Theorem 1.11

$\lim_{n\to\infty}a = \lim_{n\to\infty}b$ implies $a=b$

Mulitplication of Cauchy sequences is well defined

Computation Verification (Kähler Geometry)

Tautology question

Proof Verification For A Proof That The Domain Of An Inverse Function = Range Of Original Function

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