Isosceles Triangle Perimeter Formula

An isosceles triangle is said if it has two equal sides and two equal internal angle. While, the perimeter of an isosceles can be found, if the base and sides are known. 

Formula of Isosceles Triangle Perimeter

\[\large Perimeter\;of\;Isosceles\;Triangle,P=2\,a+b\]

a = length of the two equal sides
b = Base of the isosceles triangle

Solved Example

Question 1: What is the perimeter of an isosceles triangle when a = 9 cm and b = 6 cm ?


a = 9 cm
b = 6 cm

Perimeter of an isosceles triangle = 2a + b
= 2(9) + 6
= 18 + 6 cm
= 24 cm

Practise This Question

In Fruendlich Isotherm, the value of 1n is