Area of a triangle
Area A =
1 / 2
x b x h =
b x h / 2

CB = base = b
h = height

Example

ABC is a triangle with a base b = 5 cm and a height h = 2 cm
Area A of a triangle ABC =
b x h / 2
=
5 x 2 / 2
= 5 cm²

Calculate the area of a triangle

Base
Height
Area of the triangle

Definition of a triangle

A triangle is a polygon having three sides.
A triangle is a shape with three angles and three sides. It is a three-sided polygon that consists of three edges and three vertices.

To find the area of a triangle, multiply the base by the height and then divide by 2.
The area of a triangle is half the base times the height.

Properties of a triangle

A triangle has three sides, three angles, and three vertices. It is a polygon with three edges and three vertices.
The sum of the three interior angles of a triangle is always 180°.
The area of a triangle is equal to half of the product of its base and height.
The sum of the length of the two sides of a triangle is greater than the third side. The sum of the length of any two sides of a triangle is always greater than the third side.
Interior angles of a triangle will be greater than 0° and less than 180°.
The side opposite to the largest angle is the largest side of the triangle.

Types of triangles

An isosceles triangle

An isosceles triangle is a triangle having two sides of the same length.
If a triangle is isosceles then its two angles at the base are equal.
If a triangle has two equal angles, then it is isosceles.

An equilateral triangle

In an equilateral triangle, all three angles are equal and measure 60°. An equilateral triangle is a triangle that has all its sides equal in length.

A right triangle

A right triangle (American English) or right-angled triangle (British) is a triangle in which one angle is a right angle (90°).
A right triangle is a triangle having two perpendicular sides.

A scalene triangle

A scalene triangle is a triangle which has no equal sides. It has no equal sides and no equal angles.

An acute Triangle

An acute triangle (or acute-angled triangle) is a triangle which has three acute angles (less than 90°).

An obtuse triangle

An obtuse triangle (or obtuse-angled triangle) is a triangle which has an angle greater than 90°.

To go further

A circumcircle is the circle drawn with the circumcentre as the centre and the distance between the circumcentre and any one of its vertices of the triangle as the radius.