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Numerade Educator



Problem 7 Medium Difficulty

Calculate the first eight terms of the sequence of partial sums correct to four decimal places. Does it appear that the series is convergent or divergent?
$ \displaystyle \sum_{n = 1}^{\infty} \sin n $


It appears that the series is divergent.


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Video Transcript

let's find the first aid terms of the sequence of partial songs. So that's S one as two as three. I have to write all these out because we will need all these and as a now, by definition, we know us and is just the sum of the terms and from your starting point. So in this case, a one all the way up to an now for us one, this is just the first term which is signed one. It's as two sign one plus sign, too, and so on and then sign a will go all the way up to sign of as they will go all the way to sign eight. Now we'LL go to the computer software to approximate each of these toe form decimal places as required. So the first one is just this some just one term here. So let's go ahead and find that sign of one says you can see the signal notation We're just adding from one toe one. So this is just sign of one, and then we have point eight four one five, so that would be our first term for the second. Now, this time I'LL come back and make sure that I add in two terms. So now this time you see the sum goes from one to two you have one seven five o a one point seven five o eight. Then we'LL go to three terms. This time we have one point eight nine one nine. Now we go to us for adding the first four terms a one a two, a three and a four. We get one point one three five one now going to five. Actually, add those first five terms will be able to see in our signal notation that we are adding up to five terms there and we get one seven, six two. Now we go to six but adding the first six terms of the Siri's and we have negative point one o three three now going to seven terms point five five three seven five five three seven after the decibel and then the very last term is when we add first aid, those will be able to see and our signal notation. We're adding the essay here. All elements we have won point five four three one. So let's recheck that one point five four three one. So this answers the first part of the question. This is the sequence as one through s eight and then we rounded off tow for decibels four points after the decibel. Now let's go to the second part of the question. Does it appear that this Siri's converge? Izzard averages. So if you look at the partial sums we jumped about point nine, then we increased a little bit history. Then we decreased decrease almost all by one, decreased a little more, became positive again increased by one. So hear this does not look like the limit will exist. And here it'll diverge. And the actual reason that diverges is that the limit of sign in is not equal to zero Khama. So it diverges. Bye, the diversions test. So this is why it's not surprising that the sequence of partial sums is acting wildly. And this is our final answer