In this publication, we will consider how to calculate the perimeter of a triangle and analyze examples of solving problems.
Perimeter Formula
Perimeter (P) of any triangle is equal to the sum of the lengths of all its sides.
P = a + b + c
Perimeter of an isosceles triangle
An isosceles triangle is a triangle whose two sides are equal (let’s take them as b). Side a, having a length different from the side ones, is the base. Thus, the perimeter can be calculated as follows:
P = a + 2b
Perimeter of an equilateral triangle
An equilateral or right triangle is called, in which all sides are equal (let’s take it as a). The perimeter of such a figure is calculated as follows:
P = 3a
Examples of tasks
Task 1
Find the perimeter of a triangle if its sides are equal: 3, 4 and 5 cm.
Decision:
We substitute the quantities known by the conditions of the problem into the formula and get:
P=3cm+4cm+5cm=12cm.
Task 2
Find the perimeter of an isosceles triangle if its base is 10 cm and its side is 8 cm.
Decision:
As we know, the sides of an isosceles triangle are equal, therefore:
P = 10 cm + 2 ⋅ 8 cm = 26 cm.