This section introduces summation notation, also known as sigma notation, which is used to represent the sum of terms in a sequence. It explains the structure of summation notation, including the lowe...This section introduces summation notation, also known as sigma notation, which is used to represent the sum of terms in a sequence. It explains the structure of summation notation, including the lower and upper limits of summation and the index of summation. Examples demonstrate how to interpret and calculate sums using this notation, making it a powerful tool for expressing long sums in a concise form.