# JavaScript: Find the area of a triangle where lengths of the three of its sides are 5, 6, 7

## JavaScript Basic: Exercise-4 with Solution

Write a JavaScript program to find the area of a triangle where three sides are 5, 6, 7.

This JavaScript program calculates the area of a triangle with sides of lengths 5, 6, and 7 using Heron's formula. It first computes the semi-perimeter (s) of the triangle, then uses it to find the area, which is logged to the console.

**Sample Solution: **

**JavaScript Code:**

```
// Define the lengths of the three sides of a triangle
var side1 = 5;
var side2 = 6;
var side3 = 7;
// Calculate the semi-perimeter of the triangle
var s = (side1 + side2 + side3) / 2;
// Use Heron's formula to calculate the area of the triangle
var area = Math.sqrt(s * ((s - side1) * (s - side2) * (s - side3)));
// Log the calculated area to the console
console.log(area);
```

Output:

14.696938456699069

**Live Demo: **

See the Pen JavaScript: Area of Triangle - basic-ex-4 by w3resource (@w3resource) on CodePen.

**Explanation:**

Calculate the area of a triangle of three given sides :

In geometry, Heron's formula named after Hero of Alexandria, gives the area of a triangle by requiring no arbitrary choice of side as base or vertex as origin, contrary to other formulas for the area of a triangle, such as half the base times the height or half the norm of a cross product of two sides.

The Math.sqrt() function is used to get the square root of a number. If the value of the number is negative, Math.sqrt() returns NaN.

**ES6 Version:**

```
// Declare constants for the lengths of the three sides of a triangle
const side1 = 5;
const side2 = 6;
const side3 = 7;
// Calculate the semi-perimeter of the triangle
const perimeter = (side1 + side2 + side3) / 2;
// Use Heron's formula to calculate the area of the triangle
const area = Math.sqrt(perimeter * ((perimeter - side1) * (perimeter - side2) * (perimeter - side3)));
// Log the calculated area to the console
console.log(area);
```

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