Sunday, 30 December 2012

real analysis - Prob. 3, Chap. 3 in Baby Rudin: If s1=sqrt2, and sn+1=sqrt2+sqrtsn, what is the limit of this sequence?

Here's Prob. 3, Chap. 3 in the book Principles of Mathematical Analysis by Walter Rudin, 3rd edition:




If s1=2, and sn+1=2+sn  (n=1,2,3,), prove that {sn} converges, and that sn<2 for n=1,2,3,.





My effort:



We can show that 2sn2 for all n=1,2,3,. [Am I right?]



Then we can also show that sn<sn+1 for all n=1,2,3,. [Am I right?]



But how to calculate the exact value of the limit? Where does this sequence occur in applications?

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