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Mathematics 9 Online
OpenStudy (marcelie):

help please 29

OpenStudy (marcelie):

OpenStudy (marcelie):

@Loser66

OpenStudy (loser66):

to me, the inside can be replace by \[(tan^{-1}(2)-tan^{-1}(1))+tan^{-1}(3)-tan^{-1}(2))+\cdots\]

OpenStudy (loser66):

So, we cancel the like terms. At the end, we have \(-tan^{-1}(1) +tan^{-1}(\infty)\) But \(tan^{-1}(1) = \pi/4 \) and \(tan^{-1}(\infty) = \pi/2\) So the answer should be \(\pi/4\) Let's wait for some others.

satellite73 (satellite73):

as we used to say "telescopes"

OpenStudy (marcelie):

telescope series?

OpenStudy (marcelie):

@Kainui

zepdrix (zepdrix):

:d

zepdrix (zepdrix):

Figure it out girl?

OpenStudy (marcelie):

oh not yet D: i skipped it lol

OpenStudy (marcelie):

@zepdrix come back online lmao

zepdrix (zepdrix):

Did you not understand what Lose did?

OpenStudy (marcelie):

no lol

zepdrix (zepdrix):

:U

zepdrix (zepdrix):

\[\rm \sum_{n=1}^{\infty}\left(Atan(n+1)-Atan(n)\right)\]Expand out the sum by inputting the n values,\[\rm =(Atan2-Atan1)+(Atan3-Atan2)+(Atan4-Atan3)+...\]

zepdrix (zepdrix):

What you should notice is that a bunch of stuff is going to cancel out,\[\rm =(\cancel{Atan2}-Atan1)+(Atan3\cancel{-Atan2})+(Atan4-Atan3)+...\]because of all the subtraction, ya?

zepdrix (zepdrix):

\[\rm =(\cancel{Atan2}-Atan1)+(\cancel{Atan3}\cancel{-Atan2})+(Atan4\cancel{-Atan3})+...\]

zepdrix (zepdrix):

There is one term in the front that doesn't cancel out with anything. And there will also be one term in the very end that doesn't cancel with anything.

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