Summation formulas are notations that represent definite integrals of a continuous, single variable function along a closed interval. The function is set to the given variables, and the results are added until the limit of the interval is reached.
There are three main parts to the summation notation, not including the summation symbol itself. The first is the function, which is located to the right of the sign. The second is the initial value of the variable, often denoted by "i" and located on the bottom of the notation sign. The final part is the last value to plug into the function. This symbol is located on top of the summation sign and is indicated by "n."