(adsbygoogle = window.adsbygoogle || []).push({}); I've just started studying college math.

I read the proof by contradiction is based on the law of excluded middle. So i tried

to make a general logic structure of this kind of demonstration to see how it could use

this law. If i'm right, of course.

Let X and Y be propositions.

1. X -> Y

2. ~Y

3. X v ~X ¹

By 1 and 3 we have:

4. Y v ~X

By 2 and 4 we have:

~X

Q.E.D.

¹ - Law of excluded middle

Is this how reductio ad absurdum is made?

I mean, generally the following statement is used:

"Suppose X is true. Then Y is true. But Y is false. So X is false."

But isn't it the same thing i just did above?

I know that, probably, i'm just talking non-sense. But even so, i think this non-sense

can help you guys to help me out with my doubts.

Anyway, thank you for the attention.

My first language is portuguese and i'm not a good english writer. So if i made any english mistakes, i apologize.

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# Trying to better understand the reductio ad absurdum

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