# JavaScript Math cos()

The JavaScript Math.cos() function returns the cosine of a specified number.

The syntax of the `Math.cos()` function is:

``Math.cos(x)``

`cos()`, being a static method, is called using the `Math` class name.

## Math.cos() Parameters

The `Math.cos()` function takes in:

• x - A number (in radians) whose cosine value is required.

## Return value from Math.cos()

• Returns the cosine of a given angle (a numeric value between -1 and 1).

## Example 1: Using Math.cos()

``````// cosine of 1 radian
var value1 = Math.cos(1);
console.log(value1); // Output: 0.5403023058681398

var value2 = Math.cos(-2);
console.log(value2); // Output: -0.4161468365471424

// Math constants can be used
var value3 = Math.cos(Math.PI);
console.log(value3); // Output: -1``````

Output

```0.5403023058681398
-0.4161468365471424
-1```

## Example 2: Using Math.cos() with degrees

``````// custom function for angle in degrees
function cos(degrees) {
var radians = (degrees * Math.PI) / 180;
}

// cosine of 57 degrees
value1 = cos(57);
console.log(value1); // Output: 0.5446390350150272

// cosine of negative degrees
value2 = cos(-180);
console.log(value2); // Output: -1

value3 = cos(360);
console.log(value3); // Output: 1``````

Output

```0.5446390350150272
-1
1```

Here, we have defined a `cos()` function that converts the degree value to radian and then passes it to `Math.cos()`.

We can define custom functions in similar ways to extend the capabilities of such built-in functions.