Math Memes

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Memes related to mathematics.

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Proof by fucking obviousness (sh.itjust.works)

submitted 3 weeks ago by silverchase@sh.itjust.works to c/mathmemes@lemmy.blahaj.zone

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[–] JeeBaiChow@lemmy.world 7 points 3 weeks ago (9 children)

It's fucking obvious!

Seriously, I once had to prove that mulplying a value by a number between 0 and 1 decreased it's original value, i.e. effectively defining the unary, which should be an axiom.

[–] friendlymessage@feddit.org 3 points 3 weeks ago* (last edited 3 weeks ago) (6 children)

So you need to proof x•c < x for 0<=c<1?

Isn't that just:

xc < x | ÷x

c < x/x (for x=/=0)

c < 1 q.e.d.

What am I missing?

[–] bleistift2@sopuli.xyz 5 points 3 weeks ago (5 children)

My math teacher would be angry because you started from the conclusion and derived the premise, rather than the other way around. Note also that you assumed that division is defined. That may not have been the case in the original problem.

[–] lseif@sopuli.xyz 2 points 3 weeks ago (1 children)

isnt that how methods like proof by contrapositive work ??

[–] bleistift2@sopuli.xyz 3 points 3 weeks ago (1 children)

Proof by contrapositive would be c<0 ∨ c≥1 ⇒ … ⇒ xc≥x. That is not just starting from the conclusion and deriving the premise.

[–] lseif@sopuli.xyz -2 points 3 weeks ago (1 children)

i really dont care

[–] bleistift2@sopuli.xyz 2 points 3 weeks ago

Then don’t get involved in this discussion.

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