April 2026
461 pages
17h 56m
English
Mathematicians borrow a symbol from the Greek alphabet for the sum of
—the capital sigma: Σ. In addition, some other “tags” are attached to the sigma:
The tags mean that the running variable i takes on all values in succession from an initial value to a final value. (It’s said to pass through the area in whole steps.) In our example, it runs from the start value 1 to the end value
. Assuming that , these are steps 1, 2, and ...
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