The Lesson
The area of a triangle is found using the formula:
In this formula, b is the length of the base of the triangle and h is the height of the triangle. The image below shows what we mean by the lengths of the bases and the height:
How to Find the Area of a Triangle
Finding the area of a triangle is easy.Question
What is the area of a triangle with a base of 5 cm and a height of 3 cm, as shown below?
Step-by-Step:
1
Start with the formula:
Area = ½bh
Don't forget: ½bh = ½ × b × h
2
Substitute the length of the base and the height into the formula. In our example, b = 5 and h = 3.
Area = ½ × 5 × 3 = 7.5 cm2
Don't forget: ½ × a number = 0.5 × a number = a number ÷ 2.
Answer:
The area of the triangle with a base of 5 cm and a height of 3 cm is 7.5 cm2."Find the Area" Widget
How to Find the Area of a Triangle Using Trigonometry
The area of a triangle can also be found using trigonometry. The area is found using the formula:
In the formula, a and b are lengths of two sides of the triangle and C is the angle between them. The image below shows what we mean by the two sides and the angle between them:
Read more about how to find the area of a triangle using trigonometry
What Is a Triangle?
A triangle is a flat shape with three straight sides and three corners (also called vertices). There are different types of triangle:What's in a Name?
A triangle has three corners and so three angles. Just as a tricycle has three wheels, and a tripod has three legs, a shape with three angles in called a triangle.Areas of Triangles and Rectangles
The area of a triangle is ½bh. The area of a rectangle is bh. The area of the triangle is half that of the rectangle with the same base length and height. Can you see from the image of a right-angled triangle below that this is the case?
What about this triangle below?
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