00:02
In this question, we are asked to write down the formula for the nth partial sum of the given series and then determine the sum of the series if it converges.
00:14
First, let's write down the first partial sum.
00:17
The first partial sum is just one term, right? it's 3 arc tan 2 minus 3 arc tan 1.
00:28
What i did, i just plugged in k equals 1, right? in the formula for the general term.
00:35
The second partial sum is the sum of the first two terms.
00:39
It's 3 arc tan 2 minus 3 arc tan 1, which is the first term.
00:46
And to that, we need to add the second term, which corresponds to k equals 2.
00:52
We'll get 3 arc tan 3 minus 3 arc tan 2.
00:59
Note that we can cancel arc tan 3, arc tan 2 here.
01:03
Then for s3, we'll get same first two terms as s2.
01:22
And there will be an extra term corresponding to k equals 3.
01:30
If we plug in k equals 3, we'll get 3 arc tan 4 minus 3 arc tan 3.
01:43
Now we can cancel 3 arc tan 3 and 3 arc tan 2.
01:50
As you can see, the remaining terms are negative 3 arc tan 1 and 3 arc tan 4.
01:57
Now we are ready to write down the nth partial sum...