- #1
Edgardo
- 706
- 17
Hi all,
I've got a question about indirect proof, whether I have understood it correctly:
a) Suppose I want to show A=>B, where A and B are two statements.
In the method of indirect proof I assume that [tex]\neg B[/tex] (not B) is true and use the given statement A to show a contradiction. Therefore, B must be true (because either B or [tex]\neg B[/tex] is true).
In short what I do:
[tex]\neg B[/tex] true (assumption) and A true (given statement) => contradiction
Is that correct?
b) Now another question:
Suppose I assume B is true (instead of [tex]\neg B[/tex] true) and use the given statement A such that it leads to a true statement like 1=1.
Have I showed anything with that?
In short what I do here:
B true (assumption) and A true (given statement) => no contradiction.
But that doesn't tell me anything, right?
I've got a question about indirect proof, whether I have understood it correctly:
a) Suppose I want to show A=>B, where A and B are two statements.
In the method of indirect proof I assume that [tex]\neg B[/tex] (not B) is true and use the given statement A to show a contradiction. Therefore, B must be true (because either B or [tex]\neg B[/tex] is true).
In short what I do:
[tex]\neg B[/tex] true (assumption) and A true (given statement) => contradiction
Is that correct?
b) Now another question:
Suppose I assume B is true (instead of [tex]\neg B[/tex] true) and use the given statement A such that it leads to a true statement like 1=1.
Have I showed anything with that?
In short what I do here:
B true (assumption) and A true (given statement) => no contradiction.
But that doesn't tell me anything, right?