I need to prove that log_(10)2 is irrational. I understand the way this proof was done using contradiction to show that the even LHS does not equal the odd RHS, but I did it a different way and wanted to check its validity!
cdcamandokwd
Answered question
2022-11-25
Alternate proof for " is irrational" I need to prove that is irrational. I understand the way this proof was done using contradiction to show that the even LHS does not equal the odd RHS, but I did it a different way and wanted to check its validity! Prove by contradiction: Suppose that is rational - that is, it can be written as
where a and b are integers. Then
Log both sides:
However we assumed that and thus we have a contradiction.
Answer & Explanation
Aileen Powers
Beginner2022-11-26Added 12 answers
As has been pointed out in comments and in another answer, . This is a rather subtle error, however there's a notable warning flag that could alert you to it: Your proof does not use the hypothesis that and are integers. This is a serious issue, because it means you've proved the (false) statement that cannot be written as a fraction - even if we let and be real, but:
Harmony Oneal
Beginner2022-11-27Added 1 answers
A proof can be carried out after modifying your calculation a bit.
Which is a contradiction when both a and b are non-zero integers. Check the colored step carefully and you will understand in which step you have made a mistake.