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title: Sigma Notation
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## Sigma Notation
Sigma Notation is a mathematical shorthand for representing large sums.
Sigma Notation is as follows
![alt text](https://github.com/TheRealSpartacus/sources/blob/master/SiGma.PNG "Sigma Notation")
where *n* is the lower limit *k* is the upper limit and *an* is the function you are summating
To evaluate a sum in Sigma notation, you first plug in all integers from the *n* to *k* to *an*, then add up all the results.
For example :
![alt text](https://github.com/TheRealSpartacus/sources/blob/master/Sigma%20Fig%201.PNG "Fig. 1")
First, you plug all integers from *n* to *k* into *an* :
![alt text](https://github.com/TheRealSpartacus/sources/blob/master/Sigma%20Fig%202.PNG "Fig. 2")
Second, you evaluate all instances of *an* :
![alt text](https://github.com/TheRealSpartacus/sources/blob/master/Sigma%20Fig%203.PNG "Fig. 3")
Last, you add all the results up, leaving you with the value of the sigma :
![alt text](https://github.com/TheRealSpartacus/sources/blob/master/Sigma%20Fig%204.PNG "Fig. 4")
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