Area of a triangle is given by Heron’s formula. Let ABC be a triangle such that the length of 3 sides of the triangle is AB = c, BC = a and AC = b. Then, the area of triangle ABC(△),
△ = √[s (s – a)(s – b)(s – c) where s is semi-perimeter calculated by (a + b + c) / 2.
In this article, we will explore the area of a triangle and practice Questions on the Area of the triangle and others in detail.
What is a Triangle?
Polygon with three sides is called a triangle. The different types of triangles include:
- Equilateral Triangle
- Isosceles Triangle
- Scalene Triangle
- Acute-Angled Triangle
- Right-Angled Triangle
- Obtuse-Angled Triangle
Formula Used
Various formulas used for calculating areas of the triangle are added in the table below:
Types of Triangles |
Formulas |
---|---|
Area of Equilateral Triangle |
(√3 / 4) a2 |
Area of Isosceles Triangle |
(b / 2) √[a2 – (b2/4)] |
Area of Scalene Triangle |
√[s (s – a) (s – b) (s – c) |
Area of Right-Angled Triangle |
(1/2) × b × h |
where,
- a is side of Equilateral Triangle
- a is equal side and b is base of isosceles Triangle
- s is Semi-perimeter of Triangle and is equal to (a + b + c)/2
- b is base and h is Height of Right Triangle
Practice Questions on Area of Triangle
Question 1: Find the area of the equilateral triangle with side length 11 units.
Solution:
Area of the equilateral triangle with side a is given by:
Area of Equilateral Triangle = (√3/4)a2
= (√3/4) 112
= (√3 / 4)(121)
= 52.4 square units
Question 2: Find the area of isosceles triangle with two sides of length 7 units and base of length 12 units.
Solution:
Area of the isosceles triangle with equal side a and base b is given by:
Area of Isosceles Triangle = (b / 2) √[a2 – (b2/4)]
= (12 / 2) √[72 – (122/4)]
= 6 √[49 – 36]
= 6√13 square units
Question 3: Find the area of the scalene triangle with sides 4, 7, 5 units.
Solution:
Area of the scalene triangle is given by:
Area of Scalene triangle = √[s (s – a) (s – b) (s – c) where, s = (a + b + c) / 2
s = (4 + 7 + 5) / 2 = 16 /2 = 8 units
= √[8 (8 – 4) (8 – 7) (8 – 5)
= √[8 × 4 × 1 × 3]
= √96 square units
Question 4: Find the area of the right-angled triangle with base and height 10 units and 5 units respectively.
Solution:
Area of the right-angled triangle is given by:
Area of Right-Angled Triangle = (1/2) × b × h
= (1/2) × 10 × 5
= 25 square units
Question 5: Calculate the area of a triangle with base 6 cm and height 8 cm.
Solution:
Area = (1/2) × base × height
= (1/2) × 6 cm × 8 cm
= 24 square cm
Question 6: The base of a triangle is 10 meters and its height is 15 meters. What is the area of the triangle?
Solution:
Area = (1/2) × base × height
= (1/2) × 10 meters × 15 meters
= 75 square meters
Question 7: Given the vertices of a triangle as (-3, 4), (1, -2), and (5, 6), determine its area.
Solution:
Use the formula for the area of a triangle given its vertices.
Area = (1/2) × |x1(y2 – y3) + x2(y3 – y1) + x3(y1 – y2)|
= (1/2) × |(-3)(-2-6) + 1(6-4) + 5(4-(-2))|
= (1/2) × |(-3)(-8) + 1(2) + 5(6)|
= (1/2) × (24 + 2 + 30)
= (1/2) × 56 = 28 square units
Question 8: Find the area of an equilateral triangle with side length 9 cm.
Solution:
Area = (√(3)/4) × side2
Area = (√(3)/4) × (9)
= (√(3)/4) × 81
= (81sqrt(3))/4
≈ 39.59 square cm
Worksheeet on Area of Triangle
Q1: Find the area of the equilateral triangle with side length 24 units.
Q2: Find the area of isosceles triangle with two sides of length 13 units and one side of length 20 units.
Q3: Find the area of the scalene triangle with sides 12, 13, 21 units.
Q4: Find the area of the right-angled triangle with base and height 11 units and 17 units respectively.
Q5: A triangle has sides of length 7 cm, 10 cm, and 14 cm. What is its area?
Q6: If the area of a triangle is 36 square inches and its base is 12 inches, what is its height?
Q7: Calculate the area of a right-angled triangle with legs measuring 3 meters and 4 meters.
Q8: Find the area of a triangle with vertices at (0, 0), (4, 0), and (0, 6).
Frequently Asked Questions
What is Area of Triangle with 3 Sides Definition?
Area of triangle with 3 sides can be defined as the area of triangle with all 3 different sides i.e., scalene triangle.
What is Formula Used to Calculate Area of Triangle with 3 Sides?
Formula used to calculate area of triangle with 3 sides is given by Heron’s formula.