Math Is Fun Forum

dangermulan1988

Member

Registered: 2011-06-11

Posts: 18

question about how to determine Tautologies, Contradictions & Continge

please delete

Last edited by iwan_ccie (2011-07-11 01:38:34)

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: question about how to determine Tautologies, Contradictions & Continge

hi iwan_ccie

first one is a contradiction

second one is a contradiction

third one is a tautology

fourth one is contingent

and the fifth one is also contingent.

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“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: question about how to determine Tautologies, Contradictions & Continge

hi iwan_ccie

there are several ways to determine if a proposition is a tautology or a contradiction.
the easiest one is to make a table,make columns for all the boolean variables and then plug them into the equation and if the equation is always true then it is a tautology,and if it is always incorrect than it is a contradiction.
the other one works only when you have to prove that it is a tautology.it is called reductio ad absurdum.

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

dangermulan1988

Member

Registered: 2011-06-11

Posts: 18

Re: question about how to determine Tautologies, Contradictions & Continge

Thanks for your answer!

So you created truth tables?
Can you show me how you did this? And how you determined the answers?