![]() ![]() ![]() However, since Sigma notation will usually have more complex expressions after the Sigma symbol, here are some further examples to give you a sense of what is possible: That covers what you need to know to begin working with Sigma notation. The “starting term number” need not be 1. In such cases, just as in the example that resulted in a bunch of twos above, the term being added never changes: Note that it is possible to have an index variable below the Sigma, but never use it. If the index variable appears in the expression being summed, then the current term number should be substituted for the index variable: This variable is called the “index variable”. To facilitate this, a variable is usually listed below the Sigma with an equal sign between it and the starting term number. ![]() Sigma notation is most useful when the “term number” can be used in some way to calculate each term. Sigma notation, or as it is also called, summation notation is not usually worth the extra ink to describe simple sums such as the one above… multiplication could do that more simply. All that matters in this case is the difference between the starting and ending term numbers… that will determine how many twos we are being asked to add, one two for each term number. In the example below, the exact starting and ending numbers don’t matter much since we are being asked to add the same value, two, repeatedly. The Sigma symbol can be used all by itself to represent a generic sum… the general idea of a sum, of an unspecified number of unspecified terms:īut this is not something that can be evaluated to produce a specific answer, as we have not been told how many terms to include in the sum, nor have we been told how to determine the value of each term.Ī more typical use of Sigma notation will include an integer below the Sigma (the “starting term number”), and an integer above the Sigma (the “ending term number”). It corresponds to “S” in our alphabet, and is used in mathematics to describe “summation”, the addition or sum of a bunch of terms (think of the starting sound of the word “sum”: Sssigma = Sssum). The Sigma symbol,, is a capital letter in the Greek alphabet. ![]()
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