Question

What does this sign mean? What is it used for?

Answer 1

\[\int\limits\]

Answer 2

That is an integral sign, it is one of the fundamental building blocks of calculus.

Answer 3

What do you use it for?

Answer 4

Have you learned calculus yet?

Answer 5

Im just curious. I love learning new things. Like higher level

Answer 6

Well, when it is a definite integral you can use it to find the length of curves. Area beneath curves. Surface area, volume.
You font use it in anything but calculus.

Answer 7

Won't*

Answer 8

Oh thanks man. So every time you see an integral sign you think of curves and areas and stuff?

Answer 9

Kinda... it has tons of purposes. but it isn't something you will use in algebra or basic geometry.

Answer 10

I'm sure. But meh...

Answer 11

@Luis_Rivera I really couldn't think of another name. I swear its not a prank.

Answer 12

Ans what does this mean? \[\sum\]

Answer 13

Now I know it a prank.

Answer 14

-.-

Answer 15

Can you please tell me?

Answer 16

If you want the basis for things involving integration, you have to go back to Riemann sums and limits, I think! And work your way back from there until you find something you know or can learn.

Answer 17

That symbol is the Greek letter "sigma," uppercase, I believe. It is used to symbolized a patterned summation. Adding a bunch of terms that have a pattern.

Answer 18

Thank you @theEric unlike some people cough cough that dont wanna help me

Answer 19

I'm procrastinating / letting my mind cool down; I have time! Want a better understanding of that last symbol through an example?

Answer 20

Yes please :)

Answer 21

Alright, first we'll look at a normal summation with a pattern (that's what inspires the fancy "summation notation" that uses your symbol).

\[1+2+3\]

Answer 22

Nah, too easy... And not telling enough....
\[2+4+6\]

Answer 23

lol im listening :)

Answer 24

So, that's easy, right? So is the summation notation if you know how to read it!

I hope you see a nice pattern. If not, that's okay, here it is: 2*1 + 2 * 2 + 2 * 3.

For the picture, start from the bottom. When I say "variable," I suppose you know algebra and it's usually an "i".

\[\sum _{i=1} ^{3}{2i}\]

Answer 25

The sigma symbol is for the summation of series in most cases.
It is normally shown with n=(some number) below it, and above it is a number that indicates the number of iterations that you make the sum.
I would go into greater detail if I werent on my phone.

Answer 26

Let me know if you have any questions.

Answer 27

i = imaginary number right?

Answer 28

Wait, considering austinL's answer, I might have made a mistake... Let me check.

Answer 29

Wikipedia back's my response up.

http://en.wikipedia.org/wiki/Summation#Capital-sigma_notation

Answer 30

Haha, it is! So I guess, for clarity, we should use another letter.. Whatever we use should be a variable!

Answer 31

"i" is just very commonly used.

Answer 32

In many math applications, you are right. Commonly, \[i=\sqrt{-1}\]

Answer 33

you cant find the square root of a negative.

Answer 34

That's not what the summation notation is going for, though.

Answer 35

Yup! That's why they say it's "imaginary." It's not a "real number." You can have n\[i^2\] as a real number though.

Thank goodness, too.

Answer 36

yup