- #1
Alpharup
- 225
- 17
I am using Spivak calculus. Now Iam in the chapter limits. In pages 97-98, he has given the example of Thomaes function. What he intends to do is prove that the limit exists.
He goes on to define the thomae's function as
f(x)=1/q, if x is rational in interval 0<x<1
here x is of the form p/q where p and q are integers and q>0
f(x)=0, if x is irrational
He proves that the limit of f(x) as x tends to a(it is between 0 and 1) is 0
a can be either rational or irrational
He starts the argument like this. He assumes a natural number n so large such that (1/n)<=€, ie..(1/n) is lesser than or equal to epsilon.
Since, L =0 ( The assertion he gives on value of this limit),
he writes that |f(x)-L| or |f(x)-0|<€,
He says that the numbers x which don't satisfy this inequality are...
1/2,
2/3
1/4,
3/4,
1/5,..
and he also includes
1/n...(n-1)/n..
My doubt is how?
Why don't these numbers satisy/ why is it false?
For example, consider x=1/n
so, f(x)=1/n
|1/n|<€. Is it not true? Isn't the inequality true?
Wont it lead to contradiction?
Where have I gone wrong?
He goes on to define the thomae's function as
f(x)=1/q, if x is rational in interval 0<x<1
here x is of the form p/q where p and q are integers and q>0
f(x)=0, if x is irrational
He proves that the limit of f(x) as x tends to a(it is between 0 and 1) is 0
a can be either rational or irrational
He starts the argument like this. He assumes a natural number n so large such that (1/n)<=€, ie..(1/n) is lesser than or equal to epsilon.
Since, L =0 ( The assertion he gives on value of this limit),
he writes that |f(x)-L| or |f(x)-0|<€,
He says that the numbers x which don't satisfy this inequality are...
1/2,
2/3
1/4,
3/4,
1/5,..
and he also includes
1/n...(n-1)/n..
My doubt is how?
Why don't these numbers satisy/ why is it false?
For example, consider x=1/n
so, f(x)=1/n
|1/n|<€. Is it not true? Isn't the inequality true?
Wont it lead to contradiction?
Where have I gone wrong?
Last edited: