How to find the perimeter of a triangle?

Perimeter of a triangle = Sum of the distance of all the sides                                                                                                       

                                     = AB length + BC length + CA length

                                     = a + b + c

There are three types of triangles according their side lengths(or angle sizes).They are Scalene Triangle, Isosceles Triangle and Equilateral Triangle.

Scalene Triangle

• No sides are equal in length.
• No angles are equal in size.

Therefore; AB length ≠ BC length ≠ CA length.

Perimeter of a scalene triangle =  AB length + BC length + CA length

 Perimeter of a scalene triangle  = a+b+c 

Isosceles Triangle

• Two sides are equal in length.
• Two angles are equal in size.

Therefore; AB length = AC length  ≠ BC length.

Perimeter of a isosceles triangle =  AB length + BC length + CA length

                                                    = a + b + c

As AB length = CA length; a = c;

                                                    = a + b + a

 Perimeter of a isosceles triangle  = 2a+b 

Equilateral  Triangle

• All sides are equal in length.
• All angles are equal in size.

Therefore; AB length = BC length = CA length.

Perimeter of a quadrilateral triangle = AB length + BC length + CA length

                                                          = a + b + c

As AB length = BC length = CA length; a = b = c;

                                                          = a + a + a

 Perimeter of equilateral triangle = 3a