# CoffeeScript Math - acos()

## Description

The acos() method accepts an number and returns its arc-cosine in radians. It returns a numeric value between 0 and pi radians for x between -1 and 1. If the value of number is outside this range, it returns NaN.

## Syntax

Given below is the syntax of acos() method of JavaScript. We can use the same method in the CoffeeScript code.

```Math.acos( x )
```

## Example

The following example demonstrates the usage of the acos() method in CoffeeScript. Save this code in a file with name math_acos.coffee.

```value = Math.acos -1
console.log "The arc cosine value of -1 is : " + value

value = Math.acos null
console.log "The arc cosine value of null is : " + value

value = Math.acos 20
console.log "The arc cosine value of 20 is : " + value
```

Open the command prompt and compile the .coffee file as shown below.

```c:\> coffee -c math_acos.coffee
```

On compiling, it gives you the following JavaScript.

```// Generated by CoffeeScript 1.10.0
(function() {
var value;

value = Math.acos(-1);

console.log("The arc cosine value of -1 is : " + value);

value = Math.acos(null);

console.log("The arc cosine value of null is : " + value);

value = Math.acos(20);

console.log("The arc cosine value of 20 is : " + value);

}).call(this);
```

Now, open the command prompt again, and run the CoffeeScript file as shown below.

```c:\> coffee math_acos.coffee
```

On executing, the CoffeeScript file produces the following output.

```The arc cosine value of -1 is : 3.141592653589793
The arc console value of null is : 1.5707963267948966
The arc cosine value of 20 is : NaN
```
coffeescript_math.htm