sum function performs summation of a sequence or convergent infinite series.
The variable n is used to step through the elements of the series (default range from infinity). You can control the range and step size for n in the same way as the free variable "a". The step size must be an integer and defaults to 1. Examples:
| y=sum(1/2^n) | = 1/2 + 1/4 + 1/8 + … | = 1 |
| y=sum(1/2^n) {n:0,2} | = 1 + 1/2 + 1/4 | = 1.75 |
| y=sum(1/2^n) {n:2, } | = 1/4 + 1/8 + 1/16 + … | = 0.5 |
| y=sum(1/2^n) {n:1,,2} | = 1/2 + 1/8 + 1/32 + … | = 0.6666… |
| y=sum(1/2^n) {n:0,,2} | = 1 + 1/4 + 1/16 + … | = 1.333… |
You can also invoke the sum function in standard mathematical notation using the capital Greek letter sigma (Σ). Note that in this case you may still need to use parentheses to clarify exactly which expression is to be summed, if it has multiple terms. For instance,
y = Σ 1/n+1 {n:1,2}
is not the same as
y = Σ (1/n+1) {n:1,2}
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