What is this notation called?

Question

$$1 + 2 + \cdots + n = \frac{n(n+1)}{2}.$$ I don't need an explanation of the formula. I just want a reference for what the symbols mean.

Answer 1

It sounds like you are just having difficulty interpreting the equation because of an error in MathJax rendering on your side.

To us, the equation displays as

$$1 + 2 + \cdots + n = \frac{n(n+1)}{2}$$

Screengrabbing this and rendering it as a picture this is:

Assuming MathJax is rendering correctly, the two above look identical.

In ascii, this could be written as 1 + 2 + ... + n = n(n+1)/2

In words, this is "The sum of the first n natural numbers is equal to the expression n times the number one larger than n all divided by two."

For information on how to type in MathJax and $\LaTeX$, again visit this page. For information on how to get it to correctly render, try using a different or more up to date browser. If still having difficulty, try asking on Meta for more help.

Answer 2

It is saying that the sum $1$+ $2$ + $3$+,,, all the way to plus $n$ is equal to half of $n(n+1)$

For example,

$$1+2+3+...+98+99+100=\frac{100(101)}{2}=5500$$

What part do you need more information about?