Summations

Summation is the addition of a set of numbers; the result is their sum or total. An interim or present total of a summation process is termed the running total. The "numbers" to be summed may be natural numbers, complex numbers, matrices, or still more complicated objects. An infinite sum is a subtle procedure known as a series. Note that the term summation has a special meaning in the context of divergent series related to extrapolation. - Wikipedia

Summations are often used in the process of reducing complex equations in to smaller factors that can be more easily manipulated for operations in calculus and other mathematical methods.

Finite
RF Cafe: Summations

RF Cafe: Summations

RF Cafe: Summations

RF Cafe: Summations

Infinite
RF Cafe: Summations

RF Cafe: Summations