# radians()

Let's prepare ourselves to work with waves. But before we dive into the fun part, we have to take a look on radians.

The word itself reveals it's meaning: Radians is the count of radii.

Try to imagine the circumference of a circle as a straight line: The radius of the same circle would fit 6 times into the circumference. To say it in Processing:

`radians(360) = 6.2831855.`

The half of the circumference 360 is 180 and the radians of 180 is `3.1415927`

. Sounds familiar? `3.1415927`

is PI (π).

Therefore the radians-function converts degree-values into radian-values.

All trigonometric work with radians-values.

```
sin(radians_value);
```

```
cos(radians_value);
```

```
tan(radians_value);
```

## PI (π)

general description, what is it and what is it for

PI is a constant number that describes the ratio between the diameter and the circimference of a circle. PI is exactly 3.14159265359.

$$PI * diameter = circumference/2$$

In Processing, PI is defined as a constant and can be used by calling `PI`

. Furthermore P5 holds some more constants related to PI: `HALF_PI`

, `QUARTER_PI`

, `TWO_PI`

, `PI`

particular function / technique description with code and comments