Sigma Notation

    In order to understand Riemann sums and integration theory correctly it is important to understand summations using sigma notation.

Definition (Sigma Notation) If sigma notation _gr_1.gif] sigma notation _gr_2.gif] sigma notation _gr_3.gif] sigma notation _gr_4.gif] are real numbers such that sigma notation _gr_5.gif] then the summation of these numbers written in sigma notation is

sigma notation _gr_6.gif]

and also using functional notation,

sigma notation _gr_7.gif]

where sigma notation _gr_8.gif] The sigma notation _gr_9.gif] is called the index of summation, the sigma notation _gr_10.gif] is called the sigma notation _gr_11.gif]th term of the sum, and the upper and lower bounds of the summation are sigma notation _gr_12.gif] and sigma notation _gr_13.gif] respectively.

Example (Sigma Notation) Write the sum sigma notation _gr_14.gif] in expanded form.

    Solution. In expanded form, the sum is

sigma notation _gr_15.gif]

sigma notation _gr_16.gif]

sigma notation _gr_17.gif]

sigma notation _gr_18.gif]
sigma notation _gr_19.gif]

Example (Sigma Notation) Write the sum sigma notation _gr_20.gif] in expanded form.

    Solution. In expanded form, the sum is

sigma notation _gr_21.gif]

sigma notation _gr_22.gif]

sigma notation _gr_23.gif]

sigma notation _gr_24.gif]
sigma notation _gr_25.gif]

Example (Sigma Notation) Write the sum   sigma notation _gr_26.gif] in sigma notation.

    Solution. We find that
    
sigma notation _gr_27.gif]
sigma notation _gr_28.gif]

Example (Sigma Notation) Write the sum sigma notation _gr_29.gif] in sigma notation.

    Solution.  In sigma notation, we have

sigma notation _gr_30.gif]
sigma notation _gr_31.gif]

Example (Sigma Notation) Write the sum

sigma notation _gr_32.gif]

in sigma notation.

    Solution. We find that
    
sigma notation _gr_33.gif]
    
sigma notation _gr_34.gif]
sigma notation _gr_35.gif]

Example (Sigma Notation) Write the sum

sigma notation _gr_36.gif]

in sigma notation.

    Solution. We find that

sigma notation _gr_37.gif]

sigma notation _gr_38.gif]

sigma notation _gr_39.gif]

Cite this as:
Sigma Notation
Published by Library of Math -- Online math organized by subject into topics.
Written by Smith, David A.
http://www.libraryofmath.com/sigma-notation.html
 
    
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