MHB Intro to Logic (prove sequents)

Thread starter kk12
Start date May 8, 2019
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Intro Logic

AI Thread Summary

The discussion focuses on proving specific logical sequents, with participants expressing difficulty in starting the proofs. The first sequent involves demonstrating the relationship between existential and universal quantifiers. The second sequent requires proving the negation of an existential statement based on a universal condition. The third sequent connects the existence of a property with its implication to another property. Overall, the thread emphasizes the challenges of understanding and applying logical proofs in formal logic.

May 8, 2019

kk12

I am stuck on these questions and don't really know how to start/solve them.
prove the following sequent:
1. $(\exists x) Fx \to (\forall x) Gx \vdash (\exists x)(Fx \to (\forall x)Gx)$

2. $(\forall x)(Fx \to (\forall y)\neg Fy) \vdash \neg(\exists x)Fx$

3. $(\exists x)Fx, (\forall x)(Fx \; à \; Gx) \vdash (\exists x)G$

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May 9, 2019

Evgeny.Makarov

Gold Member

MHB

See this https://driven2services.com/staging/mh/index.php?threads/29/.

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