How to Approach a Logic Proof Involving Conditionals?

[averyjedwards2]

hi! I've been studying formal proofs for my logic final and i had a question on this one that i found in my textbook:
1.)~P\supset(horseshoe)U
2.)P\supsetF
3.)F\supsetU\thereforeU

i just have had a little trouble in the past getting started with proofs. Can anyone give me a little push and maybe start me out with this proof? thank you!

 

[Evgeny.Makarov]

Re: Formal Proofs Help!

Hi!

First, since you are already using LaTeX commands, I suggest enclosing your formulas in dollar signs. Note, however, that tokens that start with a letter must be separated from a previous command (that start with a backslash) with a space. For example, F should be separates from the preceding \supset, which gives $\supset F$. Otherwise, \supsetF will be considered as one undefined command.

Second, I am not sure what your problems are about: sets, propositional logic or something else. Please describe the context and the notations used, such as ~, $U$ and $F$.

 

[averyjedwards2]

Re: Formal Proofs Help!

okay thanks for the help! also I'm working on proving this using the 19 rules of inference

 

[Evgeny.Makarov]

Re: Formal Proofs Help!

I'm working on proving this using the 19 rules of inference

This helps, but you have not answered other questions.

 

[solakis1]

Re: Formal Proofs Help!

hi! I've been studying formal proofs for my logic final and i had a question on this one that i found in my textbook:
1.)~P\supset(horseshoe)U
2.)P\supsetF
3.)F\supsetU\thereforeU

i just have had a little trouble in the past getting started with proofs. Can anyone give me a little push and maybe start me out with this proof? thank you!

You mean Given :

1. ~P=>U

2. P=>F

3. F=>U ,then prove U

4. ~U..............ASSUMPTION for contradiction