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JEE Main 2026 Preparation: Question Papers, Solutions, Mock Tests & Strategy Unacademy » JEE Study Material » Mathematics » Heron’s formula for class 9

Heron’s formula for class 9

Heron’s formula is a geometric method to compute the area of a triangle and it is useful for computing areas of irregular shapes.

Table of Content
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Heron’s formula (also known as Hero’s formula) gives the area of a triangle when the lengths of all three sides are known in geometry. It is named after Hero of Alexandria. Unlike previous triangle area formulas, no angles or other distances in the triangle must be calculated first.

It’s used to calculate the area of various triangles, including equilateral, isosceles, and scalene triangles, as well as quadrilaterals. When the sides of a triangle are known, we may apply Heron’s formula to calculate the area. The area of the triangle is calculated using Heron’s formula with the triangle’s semi-perimeter and side lengths.

Table of content

  1. Definition:- 
  2. History of Heron’s Formula:-
  3. Mathematical Statement:-
  4. Triangle’s Area According to Heron’s Formula:-
  5. Area of Equilateral Triangle by Heron Formula:-
  6. Important notes on Heron’s Formula:-
  7. Application of Heron’s Formula:- 
  8. Conclusion
  9. FAQs

Definition:-

When the lengths of all of a triangle’s sides are known, Heron’s formula is used to find the area of the triangle, as well as the area of quadrilaterals. Hero’s formula is another name for it. This formula for calculating the area of a triangle is independent of the triangle’s angles. It is totally determined by the lengths of all triangle sides. It bears the letter “s,” which stands for semi-perimeter, which is obtained by halves a triangle’s perimeter. Similarly, the principle of determining the area is extended to determine the area of quadrilaterals.

History of Heron’s Formula:-

Heron of Alexandria penned Heron’s formula about 60 CE. He was a Greek engineer and mathematician who calculated the area of a triangle using only the lengths of its sides and went on to calculate the areas of quadrilaterals using the same method. This formula was used to prove trigonometric laws such as the Laws of Cosines and the Laws of Cotangents.

Mathematical Statement:-

According to Heron’s formula, the area of any triangle having lengths a, b, c, and ‘s’ as semi-perimeter of the triangle is determined using the below-given formula: 

 

Triangle’s Area According to Heron’s Formula:-

The following are the steps to use Heron’s formula to calculate the area:

  • Calculate the perimeter of the triangle.
  • Halve the perimeter to find the semi-perimeter.
  • Using Heron’s formula √{s(s – a)(s – b)(s – c)}, calculate the triangle’s area.
  • After you’ve determined the value, write the unit at the end (For example, m², cm², or in²).

 

Area of Equilateral Triangle by Heron Formula:-

All of the sides of an equilateral triangle are the same length. As a result, the lengths of all sides are equal in this example. Assume that the length of all sides is “a,” the semi-perimeter is “s,” and the equilateral triangle’s area is “A.” As a result, the triangle’s semi-perimeter is s=a+ a+ a ⁄ 2=3a ⁄ 2 .

So area of the equilateral triangle is determined by;

Important notes on Heron’s Formula:-

  • When all of a triangle’s sides are known, Heron’s formula is used to calculate its area.
  • By dividing the quadrilateral into two triangles, we can apply Heron’s formula to get the area.
  • The triangle’s semi-perimeter and side lengths are used in the formula.

 

Application of Heron’s Formula:-

Heron’s formula can be used in a variety of situations. They are as follows:

  • If the lengths of the different sides of a triangle are known, it can be used to calculate their area.
  • If the lengths of all of the quadrilateral’s sides are known, it can be used to calculate its area.
  • The area of any irregular quadrilateral can be calculated using Heron’s formula by turning the quadrilateral into triangles.

 

Conclusion:

Heron’s formula is a formula for calculating the area of a triangle in terms of the lengths of its sides that is credited to Heron of Alexandria (c. 62 CE). If the lengths of the sides are a, b, and c in symbols, then:

A = √{(s – a)(s – b)(s – c)} , where s is half the perimeter, or (a + b + c)/2.

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Frequently asked questions

Get answers to the most common queries related to the JEE Examination Preparation.

What is Heron’s Area of Triangle Formula?

Ans: When the lengths of all triangles are known, Heron’s formula is used to calculate the...Read full

What Is Heron’s Formula and How Does It Work?

Ans Heron’s formula is based solely on a triangle’s semi-perimeter and the lengths of it...Read full

Who Was the First to Discover Heron’s Formula?

Ans: Heron of Alexandria (also known as Hero of Alexandria) was a Greek Engineer and Mathema...Read full

How do you calculate Heron’s formula?

Ans: Using the Pythagoras theorem, the area of a triangle formula, and algebraic identities...Read full

Using Heron’s Formula, how do you find the area of a trapezium?

Ans: By drawing a perpendicular from one of the top vertices to the base, we may calculate t...Read full

Ans:

When the lengths of all triangles are known, Heron’s formula is used to calculate the area of the triangle. It can be used to calculate the areas of various triangles, including equilateral, isosceles, and scalene triangles. The semi-perimeter s = (a + b + c)/2, and area of triangle A are given as √{s(s-a)(s-b)(s-c)}, respectively, for a triangle with three sides, a, b, and c, respectively.

 

Ans

Heron’s formula is based solely on a triangle’s semi-perimeter and the lengths of its three sides. Using the lengths of the triangle’s three sides, we first calculate the value of the semi-perimeter. We can calculate the area of the shape after we have the value of the semi-perimeter.

Ans:

Heron of Alexandria (also known as Hero of Alexandria) was a Greek Engineer and Mathematician who discovered Heron’s Formula. He calculated the area of a triangle using only the lengths of its sides, allowing it to be applied to any type of triangle, including equilateral, isosceles, and scalene triangles. He extended this formula to compute the areas of quadrilaterals and proved trigonometric rules such as the Laws of Cosines and the Laws of Cotangents.

Ans:

Using the Pythagoras theorem, the area of a triangle formula, and algebraic identities, we may deduce Heron’s formula. From the top vertex to the base of the triangle, we build an attitude that divides the triangle into two triangles. We derive Heron’s formula by applying the Pythagoras theorem to both triangles and substituting the numbers obtained.

Ans:

By drawing a perpendicular from one of the top vertices to the base, we may calculate the area of the trapezium. After that, we have one parallelogram and a triangle. The area of the trapezium can be calculated by summing the areas of a parallelogram and a triangle in this situation. The area of the parallelogram may now be calculated using the formula for the area of a parallelogram or by drawing a diagonal to divide the parallelogram into two sections. We get three triangles in this situation. As a result, we use Heron’s method to compute the area of all three triangles. In either case, area values are calculated separately and then summed to determine the trapezium’s area.

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