Trigonometry Workbook For Dummies
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You can use sigma notation to write out the right-rectangle sum for a function. For example, say you’ve got f (x) = x2 + 1.

By the way, you don’t need sigma notation for the math that follows. It’s just a “convenience” — yeah, right. Cross your fingers and hope that your teacher decides not to cover the following. It can get pretty hairy.

Recall the formula for a right sum:


Here’s the same formula written with sigma notation:


Now, work this formula out for the six right rectangles in the figure below.


In the figure, six right rectangles approximate the area under


between 0 and 3.


If you plug 1 into i, then 2, then 3, and so on up to 6 and do the math, you get the sum of the areas of the rectangles in the above figure. This sigma notation is just a fancy way of writing the sum of the areas of the six rectangles.

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Mary Jane Sterling taught algebra, business calculus, geometry, and finite mathematics at Bradley University in Peoria, Illinois, for more than 30 years. She is the author of several For Dummies books, including Algebra Workbook For Dummies, Algebra II For Dummies, and Algebra II Workbook For Dummies.

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