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Area of an Equilateral Triangle

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  • Last Updated : 22 Nov, 2022
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Area of an equilateral triangle is the space occupied by an equilateral triangle. A with all sides equal and the measure of each angle being 60° is called an equilateral triangle. The area of an Equilateral triangle can be calculated by the area of the triangle formula if its base and height are given i.e. Area = 1/2 × b × h. But if only one side of an equilateral triangle is given then its area is calculated by using a specific formula which is covered in this article.

What is the Area of an Equilateral Triangle?

Area of an Equilateral Triangle is the region that is enclosed by the boundary of the triangle. Area of an equilateral triangle is measured in square units. Area of an equilateral depends upon the length of a side of an equilateral triangle. Les learn the formula used to define the area of an equilateral triangle.

Area of Equilateral Triangle

Area of an equilateral triangle is the space occupied between the sides of the equilateral triangle in a plane. For an equilateral triangle, 

Formula for finding the area of a triangle whose base and height are given is

Area = 1/2 × base × height

If only sides, of the triangle, are given. Let an equilateral triangle of side ‘a’ be given then its area is

Area = √3a2/4

Equilateral Triangle’s Area Derivation

Let’s calculate the area for a given equilateral triangle of side a. It is known that the area of a triangle is given as 1/2 × Base × Height.

equilateral triangle

 

Here the base is a. Let’s find the height of this triangle in order to find the area. It can clearly be seen that the height can be found using the Pythagoras theorem since it is one of the sides of the right-angled triangle.

Applying Pythagoras theorem,

h2 + (a/2)2 = a2

h2 = (3a2/4)

h = √3a/2

Now the height of this equilateral triangle is known. Now, substitute this value of height into our formula, 

Area = 1/2 × Base × Height = 1/2 × a × √3a/2  

Area = √3a2/4

Hence we get the area as √3a2/4.

Derivation of Area of Equilateral Triangle using Trigonometry

Suppose the sides of a triangle are given, then the height can be calculated using the sine formula. Let the sides of a triangle ABC be a, b, and the angle corresponding to them be A, B, and C. Now, the height of a triangle is

h = a × Sin B = b × Sin C = c × Sin A 

Now, area of ABC = ½ × a × (b × sin C) = ½ × b × (c × sin A) = ½ × c (a × sin B)

Since it is an equilateral triangle, A = B = C = 60° and a = b = c

Area = ½ × a × (a × Sin 60°) = ½ × a2 × Sin 60° = ½ × a2 × √3/2

Thus,

Area of Equilateral Triangle = (√3/4)a2

Perimeter of the Equilateral Triangle

An equilateral triangle is a triangle with all three sides and the perimeter of any figure is the sum of all its sides. So, the perimeter of an equilateral triangle of length a is given by 

Perimeter(P) = a + a + a = 3a

Properties of an Equilateral Triangle

An equilateral triangle is one triangle in which all three sides are equal. For an equilateral triangle PQR, PQ = QR = RP. A few important properties of an equilateral triangle are:

  • All three sides are equal in an Equilateral Triangle
  • In an equilateral triangle, all three internal angles are equal to each other and their value is 60°
  • For an equilateral triangle, the median, angle bisector, and perpendicular all are the same
  • Ortho-centre and centroid of an equilateral triangle are the same points
  • Area of an equilateral triangle is √3 a2/ 4
  • Perimeter of an equilateral triangle is 3a

Solved Examples on Area of Equilateral triangle

Example 1: Find the area of the triangle whose all sides measure 4 units.

Solution:

As given all sides are of equal length hence, we can say that it is an equilateral triangle.

So we can apply the formula to directly find the area of this triangle.

Area = √3a2/4 = √3 × 42/4 = 4√3 units2

Example 2: Find the perimeter of the triangle whose sides are given as 3 cm, 4 cm, and 5 cm.

Solution: 

Sum of all the sides of any triangle is the perimeter of triangle

Hence, the perimeter of this given triangle is (3 + 4 + 5) cm

i.e. Perimeter is 12 cm

Example 3: Find the height of the equilateral triangle whose side is 4 cm.

Solution:

The formula for the height is given by: h = √3a/2 

h = (√3 × 4)/2 = 2√3 cm

Hence the height of the triangle is 2√3 cm

Example 4: Find the perimeter and area of the equilateral triangle whose side is given as 4 cm.

Solution: 

Side (s) = 4 cm

For any equilateral triangle the perimeter is calculated as 3 × s

Primeter(P) = 3 × 4 = 12 cm

Area = √3a2/4 
        = √3(4)2/4
        = √3(16) / 4 cm2
Area = 4√3 cm2

Example 5: Find the area of an equilateral triangle when the perimeter is 18 cm.

Solution:

Perimeter of an equilateral triangle = 18 cm

Perimeter of the equilateral triangle = 3a

3a = 18, a = 6

The length of side is 6 cm.

Area, A = √3 a2/ 4 sq units

            = √3 (6)2/ 4 cm2

            = 12√3 cm2

Then area of the equilateral triangle is 12√3 cm2

FAQs on the Area of Equilateral triangle

Question 1: What is an Equilateral Triangle?

Answer:

An equilateral triangle is a special type of triangle whose all the sides are equal and all its internal angles are 60° i.e. all its angle are equal.

Question 2: What does the Area of an Equilateral Triangle mean?

Answer:

Area of an equilateral triangle is the total space occupied by an equilateral triangle in the 2-D plane. It is measured in units2

Question 3: What is the Formula for the Area of an Equilateral Triangle?

Answer:

The formula required for finding the area of an equilateral triangle is,

A = ¼(√3a2)

where,
a is the side of equilateral triangle

Question 4: What is the Formula for Perimeter of an Equilateral Triangle?

Answer:

Formula to calculate the perimeter of an equilateral triangle is given by, let the side of equilateral triangle is a units then,

Perimeter(P) = 3 × a units

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