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Sigma notation. mc-TY-sigma-2009-1. Sigma notation is a method used to write out a long sum in a concise way. In this unit we look. at ways of using sigma notation, and establish some useful rules. In order to master the techniques explained here it is vital that you undertake plenty of practice. exercises so that they become second nature.
A shorter way of writing this is to let ur represent the general term of the sequence and put Xn r=1 ur. Here, the symbol Î£ is the Greek capital letter Sigma corresponding to our letter âSâ, and refers to the initial letter of the word âSumâ. So this expression means the sum of all the terms ur where r takes the values from 1 to n. We can also write Xb r=a ur to mean the sum of all the terms ur where r takes the values from a to b. In such a sum, a is called the lower limit and b the upper limit. Key Point The sum u1 +u2 +u3 +...+un is written in sigma notation as Xn r=1 ur. c mathcentre July 18, 2005 2