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# JavaScript Math cos: Complete Guide

The Math.cos() function in Javascript is used to return the cosine of that number. This method comes in handy in programming contexts dealing with any trigonometric expressions.

## JavaScript Math cos()

Javascript math cos() is a built-in function used to find the cosine value of the given number. Since cos() is a static method of Math, it can be used without creating an object.

The Javascript cos() method returns the numeric value between -1 and 1, representing the cosine of an angle given in radians.

To find the cosine value of a given argument in JavaScript, the Math.cos() method is used.

### Syntax

```Math.cos(x)
```

### Parameter(s)

The variable x (in radians) whose cosine value is to be determined.

### Return Value

```The cosine value between -1 and 1.
```

See the following figure.

#### Note:

• If the passed value is empty, this method returns NaN.

### Compatibility:

• Internet Explorer
• Firefox
• Opera
• Safari
• Android webview
• Chrome for Android
• Firefox for Android
• Opera for Android
• Safari on iOS
• Samsung Internet
• Node.js

JavaScript version: ECMAScript 1

Consider the following examples.

### example1.js

The following code example demonstrates the use of the Javascript cos() method.

```//example1.js

let a = 0;
let b = 1;
let c = Math.PI;
let d = 2 * Math.PI;

console.log(Math.cos(a));
console.log(Math.cos(b));
console.log(Math.cos(c));
console.log(Math.cos(d));```

#### Output

```node example1
1
0.5403023058681398
-1
1
```

### Pass empty value to the cos() method(example2.js)

The following example demonstrates the case where an empty value is passed.

```// example2.js

let x;

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

#### Output

```node example2
NaN
NaN
```

### Find the sides of the triangle using cos() method

The following code example demonstrates the application of this method in a simple programming context.

Given the base angle of a triangle and the base side, find all the remaining sides of the triangle.

```// example3.js

// Given the base angle of a triangle and the base side,
// find all the remaining sides of the triangle.

let p;
let b;
let h;

let angle;

const rl = r.createInterface({
input: process.stdin,
output: process.stdout
});

const prompt1 = () => {
return new Promise((resolve, reject) => {
rl.question('Base side: ', (answer) => {
resolve();
});
});
};

const prompt2 = () => {
return new Promise((resolve, reject) => {
resolve();
});
});
};

const main = async () => {
await prompt1();
await prompt2();
rl.close();

console.log('The three sides of the triangle are:');
console.log(b); 					//base side

h = b / (Math.cos(angle));
console.log(h); 					//hypotenuse

let angle2 = (Math.PI) / 2 - angle;
p = h * Math.cos(angle2);

console.log(p); 					//third side
}

main();
```

#### Output

```Test Case 1:
->node example3
Base side: 6
The three sides of the triangle are:
6
6.928204127882605
3.464103410351597

Test Case2:
->node example3
Base side: 30
The three sides of the triangle are:
30
42.42639993882793
29.99999019615471
```

## Conclusion

If you want to find the cosine value of the given number, then use Javascript math.cos() method.