Area and Perimeter of a Triangle

Perimeter of a Triangle

The perimeter of a triangle equals the sum of the length of its three sides.

Equilateral Triangle Isosceles Triangle Scalene Triangle
Perimeter of an Equilateral Triangle Formula Perimeter of an IsoscelesTriangle Formula Perimeter of a Scalene Triangle Formula
Equilateral Triangle Isosceles Triangle Scalene Triangle

Area of a Triangle

The area of a triangle is equal to half its base times its height.

The height of a triangle is each of the perpendicular lines drawn from one vertex to the opposite side (or its extension).

Area of a Triangle

Formula for the Area of a Triangle

Example

Find the area of the triangle:

Area of a Triangle

Area of a Triangle

Area of an Equilateral Triangle

Area of an Equilateral Triangle

Height of an Equilateral Triangle Formula

Area of an Equilateral Triangle Formula

Example

Calculate the area of an equilateral triangle with a side of 10 cm.

Triangle Operations


Area of a Right Triangle

The area of a right triangle equals half the product of the legs.

Area of a Right TriangleFormula for the Area of a Right Triangle

Example

Calculate the area of the right triangle with legs measuring 3 and 4 cm.

Area of a Right TriangleTriangle Operations

Semiperimeter

The semiperimeter of a triangle equals half the sum of its sides.

It is denoted with the letter s.

Semiperimeter

Heron's Formula

Heron's formula is used to find the area of a triangle knowing the length of all three sides.

Heron's Formula

Example

Find the area of the triangle with sides measuring 3, 4 and 5 cm.

Triangle Operations

Triangle Operations


Circumscribed Circle in a Triangle

Circumscribed Circle in a Triangle

Area of a Circumscribed Circle in a Triangle Formula

R = radius of the circumscribed circle.


Inscribed Circle in a Triangle

Inscribed circle in a Triangle

Area of an Inscribed Circle in a Triangle Formula

r = radius of the inscribed circle.

s = semiperimeter

Semiperimeter


Knowing the Lengths of Two Sides and the Angle between them

Area of a Triangle

Area of a Triangle Formula