How does this "PROOF" proves the theorem?

Posted by X on Sep 12, 2013; 2:08pm
URL: http://discussion-forum.276.s1.nabble.com/How-does-this-PROOF-proves-the-theorem-tp7583937.html

This theorem is from Apostol's Mathematical Analysis (2nd ed.).

I can't understand the reasoning behind the proof.



Please help.

Thank You.