# Conditional rule

1. Sep 15, 2008

### evagelos

what is conditional rule,how is it used in:

1) propositional calculus

2) IN ordinary mathematical proofs ,examples will help

2. Sep 15, 2008

### CompuChip

In propositional calculus, A => B is equivalent to ~A v B. It's just one more of those logic operators which can be expressed in others (or: be used to express all others in). But implication is an "intuitive" rule, in the sense that it indicates something logically following from something else.

In "ordinary" mathematical proofs, it is used all the time. Open any mathematics book and it will be full of statements like "if ..., then ...", "assuming ..., we can show ...." and "from ... it follows that ....".

3. Sep 15, 2008

### evagelos

I AM sorry it was my mistake what i actually meant by conditional rule it was ;

the rule of conditional proof ,known as the DEDUCTION THEOREM in some books

thank you

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