## The Mathematical Symbol "Double Union (⋓)"

Delving into the "Double Union" Symbol (⋓): A Set Theoretical Overview

Mathematics, with its vast array of symbols, offers concise ways to represent complex operations and relationships. In the domain of set theory, the "Double Union", designated as ⋓, holds special significance.

## Unraveling the ⋓ Symbol

At its core, the ⋓ symbol is often associated with a union operation over a collection of sets rather than just two individual sets. While the regular union operation combines two sets, the double union can be used to represent the union of multiple sets, especially when working within a family of sets or a sequence of them.

Example 1:

Imagine we have a family of sets $$\{ A_i \}$$ where $$i$$ ranges from 1 to n. If we wish to represent the union of all these sets, the notation would be:

i=1n $$A_i$$

Example 2:

Let's say we're working with a sequence of sets defined by some property, such as $$B_k$$ representing all integers divisible by $$k$$. To express the union of all such sets for values of $$k$$ from 1 to m, we would denote:

k=1m $$B_k$$

The ⋓ symbol streamlines mathematical expressions, especially when dealing with infinite unions or unions over a defined index set. Understanding this symbol, along with its counterpart for intersection (⋒), is fundamental for anyone delving deeper into set theory and its applications. ## Are You Good at Mathematical Symbols?

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## Codes for the ⋓ Symbol

 The Symbol ⋓ Alt Code Alt 8915 HTML Code ⋓ HTML Entity ⋓ CSS Code \22D3 Hex Code ⋓ Unicode U+22D3

## How To Insert the ⋓ Symbol

(Method 1) Copy and paste the symbol.

The easiest way to get the ⋓ symbol is to copy and paste it into your document.

Bear in mind that this is a UTF-8 encoded character. It must be encoded as UTF-8 at all stages (copying, replacing, editing, pasting), otherwise it will render as random characters or the dreaded �.

(Method 2) Use the "Alt Code."

If you have a keyboard with a numeric pad, you can use this method. Simply hold down the Alt key and type 8915. When you lift the Alt key, the symbol appears. ("Num Lock" must be on.)

(Method 3) Use the HTML Decimal Code (for webpages).

HTML TextOutput
<b>My symbol: &#8915;</b>My symbol: ⋓

(Method 4) Use the HTML Entity Code (for webpages).

HTML TextOutput
<b>My symbol: &Cup;</b>My symbol: ⋓

(Method 5) Use the CSS Code (for webpages).

CSS and HTML TextOutput
<style>
span:after {
content: "\22D3";}
</style>
<span>My symbol:</span>
My symbol: ⋓

(Method 6) Use the HTML Hex Code (for webpages and HTML canvas).

HTML TextOutput
<b>My symbol: &#x22D3;</b>My symbol: ⋓
On the assumption that you already have your canvas and the context set up, use the Hex code in the format 0x22D3 to place the ⋓ symbol on your canvas. For example:
JavaScript Text
const x = "0x"+"E9"
ctx.fillText(String.fromCodePoint(x), 5, 5);
Output

(Method 7) Use the Unicode (for various, e.g. Microsoft Office, JavaScript, Perl).

The Unicode for ⋓ is U+22D3. The important part is the hexadecimal number after the U+, which is used in various formats. For example, in Microsoft Office applications (e.g. Word, PowerPoint), do the following:
TypeOutput
22D3
[Hold down Alt]
[Press x]

(The 22D3 turns into ⋓. Note that you can omit any leading zeros.)
In JavaScript, the syntax is \uXXXX. So, our example would be \u22D3. (Note that the format is 4 hexadecimal characters.)
JavaScript TextOutput
let str = "\u22D3"
document.write("My symbol: " + str)
My symbol: ⋓