only non-(pseudo intellectuals) will be able to prove this 1.

do your own homework brainlet

>>8769339
your notation is incomprehensible

>>8769339
prove this
[math]\dfrac{a}{b} ^{tg}*36* \sqrt[3]{b^3 - 9ac} < \dfrac{abt}{g}[/math]

>>8769339
since none of you psedo-intellectuals were able to solve it:
) 1. (x)Ax v (x)Bx // (x)(Ax v Bx)
2. ∼(x)(Ax v Bx) AIP
3. (∃x)∼(Ax v Bx) 2, QN
4. (∃x)(∼Ax * ∼Bx) 3, DM
5. ∼An * ∼Bn 4, EI
6. ∼An 5, Simp
7. (∃x)∼Ax 6, EG
8. ∼(x)Ax 7, QN
9. (x)Bx 1, 8, DS
10. Bn 9, UI
11. ∼Bn * ∼An 5, Com
12. ∼Bn 11, Simp
13. Bn * ∼Bn 10, 12, Conj
14. ∼∼(x)(Ax v Bx) 2–13, IP
15. (x)(Ax v Bx) 14, DN

>>8770289
your notation is shit, and no one cares that you're learning logic 101 brainlet faggot

>>8770289
>psedo
You may be good in math but you would fail in basic English.

>>8769339
>Can't even use alt characters
here you go brainlet:
→↔¬∧∨⊻⊤⊥∀∃≔⊢⊨

Formal logic is dumb, go try listing every functionally complete base 5 logic gate.

>>8769339
Literally no one uses (x) to mean [math]\forall x[/math] anymore. That just dates back several decades to when we hadn't come up with a good notation for this yet.

>>8770289
No one writes proofs like this unless they're in a first-year undergrad course. Here's how a "real" proof might run:
suppose the conclusion is false, i.e. [math]\neg \forall x (A(x) \lor B(x))[/math]
by definition (or axioms, depending on which symbols you take to be fundamental) this is equivalent to [math]\exists x (\neg A(x) \land \neg B(x))[/math]
clearly for that particular x, [math]A(x) \lor B(x)[/math] is false.
so [math]\forall x (A(x) \lor B(x))[/math] does not hold
the result follows by contraposition

Why do people still bother learning logic after Principia Mathematica's inevitable failure? If we know that the entire system is incapable of justifying itself or even reaching a conclusion without destroying itself, what's the point?

We learned that mesmerism could reach no conclusions and abandoned it. We learned that augury could reach no conclusions and abandoned it. We learned that miasma theory could reach no conclusions and abandoned it. Why haven't you abandoned logic yet?

>>8770437
> the entire system is incapable of justifying itself or even reaching a conclusion without destroying itself, what's the point
Popsci misunderstandings of famous results belong on >>>/reddit/.

File: respect_paid_in_full.jpg (16KB, 430x320px) Image search: [Google]

16KB, 430x320px

>>8770444
The fucking trips confirm it

>>8770426
>No one writes proofs like this unless they're in a first-year undergrad course.
but no one writes propositions using FOL notation like that anymore either, also rarely using artefacts from propositional logic like the negation and conjunction symbols. It's obvious questions like these are to train one in writing formal proofs like the one given in the post you replied to.

Also it is not """"""by definition""""""" that demorgan's law works, enabling you to bring the negation past the universal quantifier, so even if you were to write this proof in an informal manner like you have now, it would still be insufficient.