# How to Use the Math.cos() Function in JavaScript?

The `Math.cos()` function in JavaScript returns the cosine of a number. The cosine of a number is defined as the ratio of the adjacent side to the hypotenuse of a right-angled triangle.

Here’s an example of how to use the `Math.cos()` function:

``````let angle = Math.PI / 4;
let cos = Math.cos(angle);

console.log(cos);``````

This will output `0.7071067811865475`, which is the cosine of `Math.PI / 4`. The value of `Math.PI` is a constant in JavaScript that represents the mathematical constant pi.

Note that the `Math.cos()` function takes an angle in radians as its argument. To convert an angle from degrees to radians, you can use the following formula:

``let radians = degrees * (Math.PI / 180);``

So, for example, to find the cosine of an angle of `30` degrees, you can do the following:

``````let degrees = 30;
let radians = degrees * (Math.PI / 180);

console.log(cos);``````

This will output `0.8660254037844386`, which is the cosine of `30` degrees in radians.