- #1

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## Homework Statement

sum of tan(1/n)/(1+n) for n=1 to infinity

## Homework Equations

## The Attempt at a Solution

I tried using the ratio test and the comparison/limit comparison tests but can't think on anything to compare it to.

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- Thread starter kskiraly
- Start date

- #1

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sum of tan(1/n)/(1+n) for n=1 to infinity

I tried using the ratio test and the comparison/limit comparison tests but can't think on anything to compare it to.

- #2

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I'm far from a math wiz, but here's how I see it:

tan(x) will always be between -1 and 1,

but tan (1/n) will always be positive so it will be between 0 and 1

(well, actually for this problem, the max value of the numerator is tan(1) and it continues to decrease)

and the denominator will be at the very least 2 and it will continue to increase

so your fraction will continue to get smaller and smaller

in fact, it will always be smaller than 1/n

since the top will be at most 1 and the the denominator will be greater than n

so, tan(1/n)/(n+1) < 1/n

and you know that 1/n converges...so by comparison, tan(1/n)/(1+n) must also converge

tan(x) will always be between -1 and 1,

but tan (1/n) will always be positive so it will be between 0 and 1

(well, actually for this problem, the max value of the numerator is tan(1) and it continues to decrease)

and the denominator will be at the very least 2 and it will continue to increase

so your fraction will continue to get smaller and smaller

in fact, it will always be smaller than 1/n

since the top will be at most 1 and the the denominator will be greater than n

so, tan(1/n)/(n+1) < 1/n

and you know that 1/n converges...so by comparison, tan(1/n)/(1+n) must also converge

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- #3

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I'm far from a math wiz, but here's how I see it:

tan(x) will always be between -1 and 1,

Are you sure about that? What does tan(x) approach as x approaches pi/2 from the left?

- #4

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and you know that 1/n converges...so by comparison, tan(1/n)/(1+n) must also converge

The SEQUENCE with general term 1/n converges, does the series?

- #5

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Watch out for comparing to the famously DIVERGING harmonic series.

- #6

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and

"The harmonic series diverges, albeit slowly, to infinity"

http://en.wikipedia.org/wiki/Harmonic_series_(mathematics)

well...ok, I forgot about the n^r r > 1 condition for convergence

but that's why I put the disclaimer about not being a math wiz

but...BUT...the series in question does converge

<---has super maple skills

- #7

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- #8

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mybsaccownt sorry about the last post i didn't fully read your last one.

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