Sigma notation for sums | Sequences, series and induction | Precalculus | Khan Academy

Missed the previous lesson?

Precalculus on Khan Academy: You may think that precalculus is simply the course you take before calculus. You would be right, of course, but that definition doesn't mean anything unless you have some knowledge of what calculus is. Let's keep it simple, shall we? Calculus is a conceptual framework which provides systematic techniques for solving problems. These problems are appropriately applicable to analytic geometry and algebra. Therefore....precalculus gives you the background for the mathematical concepts, problems, issues and techniques that appear in calculus, including trigonometry, functions, complex numbers, vectors, matrices, and others. There you have it ladies and gentlemen....an introduction to precalculus!

About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We've also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content.

For free. For everyone. Forever. #YouCanLearnAnything

Subscribe to Khan Academy’s Precalculus channel:

[Moccasinmike]

Why can't teachers explain things this clearly?! Thank you!

[notandinotandi]

Sooo.. it's basicly a FOR loop? Nice!

[pandamoniumxP]

The way you wrote the sigma symbol was chillingly perfection.

[solo]

My Calculus teacher didn’t explain these and we have a test with them on it today. Thanks for this guide it was easy to understand and now I feel like I understand it entirely.

[muscleman]

Khan Academy would legit make any math problem look super easy in their tutorials! 10/10👋🏼

[fusion]

oh my god! index was the key word here, I couldn't understand this at all for the entirety of math class today but when watching this video my brain instantly connected the word index with a loop in java and I instantly understood the concept. Geez, it's funny how fast you can catch onto something once the right words are presented

[thorstambaugh]

I added the second series in 10 seconds. The numbers can be paired off to sum 100 1 and 99, 2 and 98, etc. There are 49 pairs plus 50 plus 100 totaling 5050. This may be done for any series with any standard linear increment

[bigbad]

I learned more watching this video than a 1hr 40min tutorial I had yesterday. Thanks

[fridahmadiba]

this video has been very helpful. thank you

[EmotionxPlayOw]

When you search for the lesson you don't understand on YouTube and multiple videos come up but you choose to watch Khan Academy.

[melissapatton]

This is so helpful. We use Prentice Hall textbooks at my school and they're basically worthless for explaining how to do problems. I've missed two days of Algebra 2 in a row and this video just brought me some hope. Thanks!

[ramelm]

float sum;
for(int i = 1; i <= 50; i ++) {
sum += 3.14i^2;
}

return sum;

[gabilovesinging]

Wow thankyou sm... I'm some one who has a lot of problems in maths but after seeing this i'm def done w sigma notation ....wow you guys should try ITS AMAZING

[ThienNguyen-phrv]

Thanks, these videos are saving my grades from the wrath of my crappy algebra 2 teacher. 

[ellaartenstein]

Thank you it’s very concise and helpful

[iVince]

Perfect timing. Just learning this now

[leadseducators-leoshe]

Salam,

I am littely crying after watching this trust me i have studied over 20 uears in colleges n unis but none had explained it please keep tuting us all and maintain your contribution to develop

[RobinSingh-mszt]

Thanks for this wonderful explanation.

[yaquanliang]

Hey may I ask does the 'i' and 'n' represent the same thing? thanks in advance!

[ellispiper]

froget all my alebra and never even took precalt, which are needed for uni stats. Thank you sir, the math aspect is all making sense