I was about to fail my Calc 2 class then I found your youtube videos. I successfully crammed for my final exam and got a B+. Hell yea, that's how we do it! Thank you!! To all my crammers/procrastinators out there, all I have to say is there is still hope.
You are a life-saver man! I can't get over how you make difficult concepts much easier. I always look to your videos for guidance. Thank you for taking the time to make these for everyone.
Professor Organic Chemistry Tutor, thank you for a fantastic explanation of Absolute Convergence, Conditional Convergence and Divergence in Calculus Two. The examples in this video, increases my full understanding of this topic in Calculus. This is an error free video/lecture on UA-cam TV with the Organic Chemistry Tutor.
For the last problem, when checking 'a sub n' after getting that '|a sub n|' was divergent, why would you include the (-1)^n when finding the limit for the alternating series? shouldn't we just try to find whether 'a sub n+1' is smaller than 'a sub n' and exclude the part that's changing the signs?
I’m so confused on that part too. And for the absolute value expression, why did he apply the alternating series test instead of the comparison test since the sign is gone?
I think tutor was confused but anyway, in last task you get 1 from limit in both cases that means it is automatically divergent by checking Alternating Series Test (does not passes 1st test).
I think he uses the alternating series test because it would be more efficient to test whether the series converges or diverges rather than taking a direct comparison, since the problem is already set up nicely for taking the alternating series test
Paid a stupid amount of tuition to get professors who can't teach for shit. Why do I even bother going to class when I have this guy explaining every single simple concepts that my professors can't
I'm confused with this as well. Of course anything with (-1)^n multiplied it isn't going to converge... That's why we have the alternating series test. Why is it that in this particular case we can just skip the test altogether? This is by far the worst part of calculus. Most of it isn't consistent. You have to rely on memory rather than math skill.
Hey you would do that (and you would be absolutely correct) if you were doing the ALTERNATING SERIES TEST. Here he used the DIVERGENCE TEST. In this case, either of those tests will work. Hope that clears it up.
I think it's because the initial limit test for An did not come up to be 0 and therefore it failed the alternate series test and he had to use divergence test.
These videos are very helpful, but one thing is not clear here 11:38 , why did he find significance in including the (-1)n as part of the sequence an while computing the limit, despite choosing to ignore it in all other examples?
arisoda - so try doing the alternating test anyways (on n^3 / n^3 +5 ) it’s going to fail. So he skipped the alternating test anyways and just went straight on doing the divergent test. He shouldn’t have done it like that because it confused me as well. The previous example would’ve have failed if he skipped the alternating test. So I get your confusion.
Faisal Kabir But how can one SKIP the alternating series test if the divergence test is part of the alternating series test and then go ahead do the divergence test. Isn't he still doing the alternating series test then anyway?
@@jamesxia9188 because /a_n/= 1/n^1/3 is the p-series so when the p is less than 1, it div. But in the other hand, the series a_n is an alternating series so he must use 2 condition to test whether this seris conv or not. The 1st conditon is the /a_n+1/ is less than or equals /a_n/ ( /a_n/ i mean the absolute value of a_n). The 2nd one is the lim of a_n (or /a_n/) when n comes to infi, equals to 0. Hope my explanation can help you ^^
Bro ig divergence test is another name for Leibnitz test. So what you do in Leibnitz test is that you check if the series is monotonically decreasing and if the limit of the series excluding the alternating part ,i.e. (-1)^n is 0. If both of these conditions satisfy then we conclude that the series or sequence is convergent
Im confused about when to take a_n and when to take the entire series with (-1)^n included. In your video you take a_n to be everything except (-1)^n, but if thats the case with an alternating series, then there's never any difference between the normal series and the absolute value of the series since you take away the thing that causes it to be alternating. How does this work?
The Alternating series test checks for three things: 1. That the series is alternating (-1)^n for example, 2. that the portion multiplying the -1^n is "bounded" that is that it is going to eventually stop growing (that's the limit=0), and 3. That the rate of change (or each subsequent term) is smaller than the previous (monotonically decreasing). If something is bounded and decreasing then it doesn't matter if the (-1)^n is there since it is adding/subtracting less and less each time towards an end and thus we can ignore the (-1)^n portion.
Knowing all this still gets me a bad grade because our Calc professor's homework and quizes never match the actual test material. Its always trick problems that I have never seen.
I could be wrong but I think the p test showed that the absolute value of a_n diverges. But as he stated at the beginning of the video we still need to test the original series to see if it's conditionally convergent or divergent.
Not sure if anybody else was confused about this like I was, but if you have 1/cube root n, can't you rewrite it as 1/n^(1/3)? He wrote that earlier and explained how it was divergent with p-series, and then rewrote it and all of a sudden it's equal to zero?
how come at 7:30 you didn't just use a p-series again? also at 11:33 I thought the (-1)^n disappeared when doing the alternating series test like it did in the example at 7:16. There is some tomfoolery going on here and I don't like it.
7:30 You only use the p-series when finding the convergence of a summation of 1/n^p and not the limit. 11:33 Again, you're finding a limit. There is no summation involved so you don't use the alternating series test (which use if there is a summation sign)
Thank you so much sir. One thing i haven't get it is how can i know when limit doesn't exist? is there any rule and what is that rule? Thanks beforehand
I'm pretty confident I'm gonna fail the exam on series. My professor went through 7 sections in a week and a half on something like series which most of us have almost no initial knowledge of. Needless to say, I'm pretty angry
hi by means of having already found the absolute value of the series to be divergent, wouldn't that automatically mean the series itself is convergent making it conditionally divergent?
To anyone seeing this 4 years later- think about it like squares and rectangles. Every square is a rectangle, but not all rectangles are squares. If a series is ABSOLUTELY convergent, then it is like a square, in the sense that is both a rectangle and a square. If we know a series is conditionally convergent, then it is like a rectangle. It is possible for it to be a square as well, or maybe it's not. That's what checking the absolute value of the series determines - whether it is a square or just a rectangle. Finally, if a series isn't conditionally convergent (keeping up with the example, imagine a different shape entirely, like a circle) then we know, by default, it is also not absolutely convergent (and therefore also not a square). And if a series isn't convergent, it must be divergent.
The original is the an. Alternating series just deals with the an, but to find if something is conditionally or absolutely convergent, we must find if it converges or diverges for the absolute value of |an| and then find if the original (an) converges or diverges using alternating series.
diverges through divergence test. but yeah it's supposed to be conv I think, he used AST for the abs cone test when that would be used to test conditionally cone
I have a question. If we find that the absolute series is convergent, then we don't have to find the convergence for the given series? Would be really helpful if anyone could answer for me.
don’t know if anyone will answer but in a problem: { (-1)^n • 1/n (pretend { is the summation symbol from 1 to infinity) i would before use the alternating series test to find it to be convergent, but now i’m learning what was just shown in this video so with that same problem it would be conditionally convergent sooo is the alternating series test just a test to use to help prove it is conditionally convergent? this might be a dumb question but should the method in this video always be used first before jumping into the alternating series test?
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I was about to fail my Calc 2 class then I found your youtube videos. I successfully crammed for my final exam and got a B+. Hell yea, that's how we do it! Thank you!!
To all my crammers/procrastinators out there, all I have to say is there is still hope.
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Professor Organic Chemistry Tutor, thank you for a fantastic explanation of Absolute Convergence, Conditional Convergence and Divergence in Calculus Two. The examples in this video, increases my full understanding of this topic in Calculus. This is an error free video/lecture on UA-cam TV with the Organic Chemistry Tutor.
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For the last problem, when checking 'a sub n' after getting that '|a sub n|' was divergent, why would you include the (-1)^n when finding the limit for the alternating series?
shouldn't we just try to find whether 'a sub n+1' is smaller than 'a sub n' and exclude the part that's changing the signs?
I’m so confused on that part too. And for the absolute value expression, why did he apply the alternating series test instead of the comparison test since the sign is gone?
I think tutor was confused but anyway, in last task you get 1 from limit in both cases that means it is automatically divergent by checking Alternating Series Test (does not passes 1st test).
I think he uses the alternating series test because it would be more efficient to test whether the series converges or diverges rather than taking a direct comparison, since the problem is already set up nicely for taking the alternating series test
Yeah because the answer of the last part would be conditionally convergent not divergent.
keep it up Sir ,this is really helpful🙌👏👏
Your videos are so helpful I will pass thanks to you
Paid a stupid amount of tuition to get professors who can't teach for shit. Why do I even bother going to class when I have this guy explaining every single simple concepts that my professors can't
11:27 you wrongly took (-1)^n in the lim an. Although it does not affect the final answer as lim would be 1 which is not equal to 0.
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if ur in a hurry listen to this video in 1.25, thats like regular speed for this guy
I listen to it in 1.5 or mostly in 2 and it seems normal
11:41 don't we have to take the limit of a(n) only without (-1)^n included ?
yes, I also think so
Yes, but here the limit is still not zero. However keep in mind to get rid of (-1)^n or (-1)^n+1 because it does not belong in An.
I'm confused with this as well. Of course anything with (-1)^n multiplied it isn't going to converge... That's why we have the alternating series test. Why is it that in this particular case we can just skip the test altogether? This is by far the worst part of calculus. Most of it isn't consistent. You have to rely on memory rather than math skill.
Hey you would do that (and you would be absolutely correct) if you were doing the ALTERNATING SERIES TEST.
Here he used the DIVERGENCE TEST. In this case, either of those tests will work. Hope that clears it up.
I think it's because the initial limit test for An did not come up to be 0 and therefore it failed the alternate series test and he had to use divergence test.
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Why are you leaving the abs for others except for(-1)^n???
This is very helpful thank you
These videos are very helpful, but one thing is not clear here 11:38 , why did he find significance in including the (-1)n as part of the sequence an while computing the limit, despite choosing to ignore it in all other examples?
Thank you so much you're great but I'm still gonna fail my sequences and series exam because all this info is way too much for me to memorize...
Thanks a lot for your videos
Thank you!
You're too good
11:30 Why is the (-1)^n not removed from the a_n for the alternating series test like the previous example?
because he was doing the divergence test instead. The alternating series test is failed.
@@rockieRAGE117 But the Divergence Test is part of the Alternating Series Test... How does that work?
arisoda - so try doing the alternating test anyways (on n^3 / n^3 +5 ) it’s going to fail.
So he skipped the alternating test anyways and just went straight on doing the divergent test. He shouldn’t have done it like that because it confused me as well. The previous example would’ve have failed if he skipped the alternating test. So I get your confusion.
Faisal Kabir But how can one SKIP the alternating series test if the divergence test is part of the alternating series test and then go ahead do the divergence test.
Isn't he still doing the alternating series test then anyway?
This video is pretty clear. However, my university textbook is like a completely different one.
Why isn't it necessary to prove convergence for the first question using limits like you do in the second one if they are both alternating series?
i think it í because we checked the series with absolute value mark and saw it is convergence => the original is convergent too.
nice work
very helpful, thank you
Nice video! Thanks!
why during the p-series test, the 1/[(3)^1/3] diverges but during Lim->∞ 1/[(3)^1/3]=0 and converges?? Please explain, I am confused!!
I have the same question, did you ever find an answer?
@@jamesxia9188 because /a_n/= 1/n^1/3 is the p-series so when the p is less than 1, it div. But in the other hand, the series a_n is an alternating series so he must use 2 condition to test whether this seris conv or not. The 1st conditon is the /a_n+1/ is less than or equals /a_n/ ( /a_n/ i mean the absolute value of a_n). The 2nd one is the lim of a_n (or /a_n/) when n comes to infi, equals to 0. Hope my explanation can help you ^^
Why isn't it An - 1 7:45? cause its the term before the last term?
7:30 Here you said "it(a_n) passes the divergence test", this confused me. Then after you found a_(n+1)
Bro ig divergence test is another name for Leibnitz test. So what you do in Leibnitz test is that you check if the series is monotonically decreasing and if the limit of the series excluding the alternating part ,i.e. (-1)^n is 0. If both of these conditions satisfy then we conclude that the series or sequence is convergent
Im confused about when to take a_n and when to take the entire series with (-1)^n included. In your video you take a_n to be everything except (-1)^n, but if thats the case with an alternating series, then there's never any difference between the normal series and the absolute value of the series since you take away the thing that causes it to be alternating. How does this work?
The Alternating series test checks for three things: 1. That the series is alternating (-1)^n for example, 2. that the portion multiplying the -1^n is "bounded" that is that it is going to eventually stop growing (that's the limit=0), and 3. That the rate of change (or each subsequent term) is smaller than the previous (monotonically decreasing). If something is bounded and decreasing then it doesn't matter if the (-1)^n is there since it is adding/subtracting less and less each time towards an end and thus we can ignore the (-1)^n portion.
Knowing all this still gets me a bad grade because our Calc professor's homework and quizes never match the actual test material. Its always trick problems that I have never seen.
Thanks man
my cal 2 exam is in 3 days😄
Thank you
Thanks to you man
We're almost done with Calculus 2! Lets goooooo
How come some times you include the (-1)^n in the a_n = statement, but other times you leave it out?
yeah I dont get that either, i thought you always ignore it for AST and ABS V test
please can you explain the convergence and divergence of improper integral
How would you solve a problem that has nsquareroot(n) instead of it being being 3squareroot(n)?
Brother at 6:21 you said p test n is less than one but how it diverge it converges as we put n from 1 to infinity?
I could be wrong but I think the p test showed that the absolute value of a_n diverges. But as he stated at the beginning of the video we still need to test the original series to see if it's conditionally convergent or divergent.
That makes sense 👍
For the last question why didn't you use AST for a_n to determine if it converged or diverged?
Not sure if anybody else was confused about this like I was, but if you have 1/cube root n, can't you rewrite it as 1/n^(1/3)? He wrote that earlier and explained how it was divergent with p-series, and then rewrote it and all of a sudden it's equal to zero?
exactly what im confused on
how come at 7:30 you didn't just use a p-series again? also at 11:33 I thought the (-1)^n disappeared when doing the alternating series test like it did in the example at 7:16. There is some tomfoolery going on here and I don't like it.
7:30 You only use the p-series when finding the convergence of a summation of 1/n^p and not the limit.
11:33 Again, you're finding a limit. There is no summation involved so you don't use the alternating series test (which use if there is a summation sign)
What about the series (-1)^n ? Its absolute value converges but the series diverges.
Thank you so much sir. One thing i haven't get it is how can i know when limit doesn't exist? is there any rule and what is that rule? Thanks beforehand
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and i have one doubt if mod an is converent and an is divergent ,what is the answer
Holy shit I was looking for economical conditional convergence ☠️☠️☠️
thanks.
I'm pretty confident I'm gonna fail the exam on series. My professor went through 7 sections in a week and a half on something like series which most of us have almost no initial knowledge of. Needless to say, I'm pretty angry
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How come in the last example we didn’t remove (-1)^n when using divergent test as we did with the second example.
You only remove (-1)^n when using an alternating series test which is only applicable for summations, and not limits
hi by means of having already found the absolute value of the series to be divergent, wouldn't that automatically mean the series itself is convergent making it conditionally divergent?
To anyone seeing this 4 years later- think about it like squares and rectangles.
Every square is a rectangle, but not all rectangles are squares.
If a series is ABSOLUTELY convergent, then it is like a square, in the sense that is both a rectangle and a square.
If we know a series is conditionally convergent, then it is like a rectangle. It is possible for it to be a square as well, or maybe it's not. That's what checking the absolute value of the series determines - whether it is a square or just a rectangle.
Finally, if a series isn't conditionally convergent (keeping up with the example, imagine a different shape entirely, like a circle) then we know, by default, it is also not absolutely convergent (and therefore also not a square).
And if a series isn't convergent, it must be divergent.
I think in example #3 you cannot use the alternating series test because it is an increasing function (n^3/(n^3+5))
its decreasing because the denominator is larger than the numerator
That's not how you determine that smh
do we solve (cos n) the same way as (cos n.pi)?
Wait why are we comparing to the original and not an? We did that for the alternating series. Why did we change it up?
The original is the an. Alternating series just deals with the an, but to find if something is conditionally or absolutely convergent, we must find if it converges or diverges for the absolute value of |an| and then find if the original (an) converges or diverges using alternating series.
What if they tell you to find absolute convergence and there is an X or (-X)^n in the series
in the last task, why lim |an| = 1 then it diverges? i think it is convergent to 1
diverges through divergence test. but yeah it's supposed to be conv I think, he used AST for the abs cone test when that would be used to test conditionally cone
Exam tomorrow.
I have a question. If we find that the absolute series is convergent, then we don't have to find the convergence for the given series? Would be really helpful if anyone could answer for me.
you still have to, "absolute convergence" means that is is convergent on both the given series and absolute series
Thank you for your response!
You don't have to as he said in the video ,hope this reply ain't too late
don’t know if anyone will answer but in a problem: { (-1)^n • 1/n (pretend { is the summation symbol from 1 to infinity) i would before use the alternating series test to find it to be convergent, but now i’m learning what was just shown in this video so with that same problem it would be conditionally convergent sooo is the alternating series test just a test to use to help prove it is conditionally convergent? this might be a dumb question but should the method in this video always be used first before jumping into the alternating series test?
breanna g i think the alternating series would just be used
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