Exercise 2.2.5

Let [ [ x ] ] be the greatest integer less than or equal to x . For example, [ [ π ] ] = 3 and [ [ 3 ] ] = 3 . For each sequence, find lim ⁡ a n and verify it with the definition of convergence.

(a)
a n = [ [ 5 ∕ n ] ] ,
(b)
a n = [ [ ( 12 + 4 n ) ∕ 3 n ] ] .

Reflecting on these examples, comment on the statement following Definition 2.2.3 that “the smaller the 𝜖 -neighborhood, the larger N may have to be.”

Answers

(a)
For all n > 5 we have [ [ 5 ∕ n ] ] = 0 meaning lim ⁡ a n = 0 .
(b)
The inside clearly converges to 4 ∕ 3 from above, so lim ⁡ a n = 1 .

Some sequences eventually reach their limit, meaning N no longer has to increase.

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2022-01-27 00:00
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