Writing Sigma Notation
Date: 02/03/99 at 09:29:38 From: Mary Kern Subject: Writing Sigma Notation I am tutoring a high school student in Integrated Math 3. She is using sigma notations in finite arithmetic and geometric series. I can help her with the equations to determine the sum, etc., but I do not understand the equation below the sign. Where does it come from? Thank you.
Date: 02/03/99 at 18:44:05 From: Doctor Cavallari Subject: Re: Writing Sigma Notation I'll try to describe what each part means and give a few examples for you. Here's one to look at for now: 7 ---- \ / 2*N ---- N=3 Sigma notation (also called summation notation) is shorthand for summing a series. The expression to the right of the Sigma is the formula that you plug each number in the series into. The equation below the Sigma (N=3 in this example) tells you two things. First, it tells you which letter (in the expression to the right) you are going to put the values into. Here, that letter is N. Second, it tells you what number to start at. So, in this example, we are going to start at the number 3 and work our way up. The number above the Sigma (7) is the number that you go up to (and include) when plugging in values. It is not necessarily the number of terms in the series. In the above example, we will input the whole numbers from 3 to 7 (3,4,5,6,7). So, our example problem will look like: 7 ---- \ / 2*N = 2*3 + 2*4 + 2*5 + 2*6+ 2*7 = 50 ---- N=3 Here is another example for you: 8 ---- \ / I+3 = 5+3 + 6+3 + 7+3 + 8+3 = 38 ---- I=5 See also: Summation notation http://www.math.uni.edu/~campbell/stat/Sigma.html - Doctor Cavallari, The Math Forum http://mathforum.org/dr.math/
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