# Variables and Arithmetic Operators

## Using Variables

In MATLAB, when you type

```myVar = 3.7;
```

in the command window, it means the variable myVar is assigned the value 3.7. You can obtain the values of your variables by typing their names:

```myVar
```
```myVar =

3.7000

```

Variable names must begin with a letter, followed by letters, numbers or underscores. MATLAB recognizes only the first 31 characters of a variable name.

## Arithmetic Operators

Basic arithmetic operations in MATLAB include six operations:

 addition + subtraction - multiplication * division / or \ exponentiation ^

Note that the right division (/) and the left division (\) do not produce the same results:

```rd = 2/5
```
```rd =

0.4000

```
```ld = 2\5
```
```ld =

2.5000

```

## Variables in Calculation

When you assign a value to a variable, it can be used in numerical calculations. For example:

```x = 2;
y = x^2;
z = y^3;
```

then you'll have z as 2^6 = 64:

```z
```
```z =

64

```

## Clearing variables

The MATLAB internal function clear will remove all variables you assigned.

```x
```
```x =

2

```
```clear
```

This is useful when you want to restart your work. In addition, it is a good idea to include clear as the first line in your script M-files (you'll learn more about this later).

## Keep in mind...

Be careful -- you should NOT use the MATLAB internal functions as the names of your variables. You will lose that function by doing so. For example, MATLAB provide the trigonometric function sine:

```sin(pi/2)
```
```ans =

1

```

(Note that the constant pi = 3.14159... is saved in MATLAB by default.)

However, if you accidentally make sin a variable by typing

```sin = 0.3333;
```

Then you will get error message next time when you want to calculate the trigonometric function sine:

```sin(pi/2)
```
```Subscript indices must either be real positive integers or logicals.

Error in ==> variables at 63
sin(pi/2)
```

That sucks, right? So you must be careful. Well, at least you can use the command clear to erase it:

```clear sin
```

This will only remove the assigned value of sin; other variables will remain unaffected.