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# Lesson 4.1: Variables

## Symbol

$\text{π pi}$
⠨⠏

## Explanation

A numeral always represents the same amount and is said to be constant. A variable is a quantity that varies in its possible value. Letters are usually used to represent variables. If a letter is used as a mathematical symbol in a mathematical context, Nemeth Code rules, rather than literary code rules, apply.

Do not use the English letter indicator before a letter that is part of a mathematical expression. Determination of use of the English letter indicator depends upon the context in which a letter appears. It does not depend upon whether a letter is used as a variable, an abbreviation, or an identifier. If it appears within a mathematical expression, the English letter indicator is not used.

Do not use the numeric indicator before a letter which represents a variable. Treat it according to the rules for letters, even though it represents a quantity.

Use the capitalization indicator, dot six, if the letter is shown capitalized. Each capitalized letter in a series of letters is preceded by dot six since each letter represents a separate and distinct value.

Space the letters as you would any number or other symbol. Do not space between a letter and the numbers associated with it. Do not space between a letter and the signs of operation with which it is applied. Use the Opening and Closing Nemeth Indicators for any letter used in a mathematical context.

When letters are adjacent to each other in a problem, as in xyz or RTS, the operation of multiplication is implied. The numerical values of each of these letters (when they are known) are to be multiplied to give a product:

if x=3,y=2 and z=5, then xyz=3×2×5=30

Do not use the numeric indicator before a letter which represents a variable. Treat it according to the rules for letters, even though it represents a quantity. When an upper case letter appears in any context, the capitalization indicator, dot six, precedes the letter. When more than one capital letter appears in a mathematical expression, each letter must be preceded by the capitalization indicator. This is because they are separate entities. The English letter indicator is not used in a mathematical context, but it is used if a single upper case letter appears in a literary context. It is not used if there is more than one adjacent upper case letter.

The lower Greek letter pi is a constant value that is approximately 3.14. However, it is often used like a variable appearing in expressions and equations as π. When pi is part of an equation, it is formatted like other variables. Pi is a two-cell symbol. The first cell is a dot four-six, the Greek letter indicator, and then the braille letter p or dots one-two-three-four.

### Example 1

$x+9$
⠭⠬⠔

### Example 2

$n-3$
⠝⠤⠒

### Example 3

$11t$
⠼⠂⠂⠞

### Example 4

$y=5$
⠽⠀⠨⠅⠀⠼⠢

### Example 5

$B+7$
⠠⠃⠬⠶

### Example 6

$\text{point}\phantom{\rule{.3em}{0ex}}C$
⠏⠕⠊⠝⠞⠀⠰⠠⠉

### Example 7

$\text{line}\phantom{\rule{.3em}{0ex}}AB$
⠇⠊⠝⠑⠀⠠⠁⠠⠃

### Example 8

$7x-2$
⠼⠶⠭⠤⠆

### Example 9

$\left(y=4\right)$
⠷⠽⠀⠨⠅⠀⠼⠲⠾

### Example 10

$\left(z/4\right)$
⠷⠵⠌⠲⠾

### Example 11

$7+\pi$
⠼⠶⠬⠨⠏