# symbol help

Discussion in 'Homework Help' started by amilton542, Dec 30, 2010.

1. ### amilton542 Thread Starter Active Member

Nov 13, 2010
494
64
some of the formulas ive been looking at are containing symbols i dont understand and there not saying what they mean
here are the symbols i dont get:

Ʃ - ive also been coming across this with a ∞ above it, does this mean infinite?
∫ - i think this means inertia but what does inertia mean? ive also seen three of these in a row one after the other, sometimes with a circle in the middle, i think that means at any point.

. - i presume the full stop is multiply ?

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Feb 19, 2010
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4. ### Georacer Moderator

Nov 25, 2009
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Σ is for sum. It usually comes with a variable term that is summed over and over.
For example $\Sigma _{\tiny{i=1}} ^{\tiny4} i=10$

$\int$ is for integration. Multiple integration signs mean integration in more than one dimension. A circle denotes integration over a closed line.
For example $\int _0 ^5 x\ dx=\left[ x^2 \right] _0 ^5=25$

As for the dot, it depends on its position in the expression. Can you be more specific?

5. ### amilton542 Thread Starter Active Member

Nov 13, 2010
494
64
thanks guys it doesnt look as scary anymore. ok i can be more specific with the . , for e.g there will be an upside down triangle . B = 0. i think i need to work on my maths, i been reading a book on magnetism and magnetic materials and its all maths way beyond me

6. ### Papabravo Expert

Feb 24, 2006
10,340
1,850
The upside down triangle is called "del" and it is a differential operator. See the following article:

http://en.wikipedia.org/wiki/Del

The interpretation depends on the thing it is applied to. This stuff isn't easy and a quick review is unlikely to be sufficient if you've never seen it before.

Last edited: Dec 30, 2010
7. ### amilton542 Thread Starter Active Member

Nov 13, 2010
494
64
ok thanks, these wikipedia print outs has provided me with more than enough for today. how long will this take to grasp to understand properly?because this does seem hard. i do about 15-20 hours a week self direct research

8. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,504
512
The sum is easy, it is basically an abbreviation.

Integral is more complex, but there are formulas that let you go from the integral to integral solution, basically someone in the past 300 years solved that particular type of integral, all you have to do is setup the integral, then look up in the list which type your integral match: http://en.wikipedia.org/wiki/Lists_of_integrals

9. ### amilton542 Thread Starter Active Member

Nov 13, 2010
494
64
are there any youtube lectures on this? i dont no what to type to find what im looking for

Feb 19, 2010
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11. ### Papabravo Expert

Feb 24, 2006
10,340
1,850
It took me about four semesters of math and physics courses to really grab onto what was happening with calculus, vectors, and vector differential operators. That is about halfway to an undergraduate degree in Electrical Engineering