Can an equilateral triangle also be isosceles?

2 Answers
Jun 4, 2018

Yes; in fact an equilateral triangle must be isosceles.


The definition of an isosceles triangle is that two of its sides have equal lengths; the case where all three sides have equal lengths is not excluded.

The definition of an equilateral triangle is that all three sides are of equal length; therefore any two sides are of equal length; and, therefore an equilateral triangle is isosceles.

Jun 4, 2018

See below.


So before we start answering the question, let start by listing the properties of both equilateral and isosceles triangle.
Equilateral triangle:
- All sides are the same length
-All angles have the same measurement
Isosceles Triangle:
-2 sides have the same length
- 2 angles have the same measurement

An equilateral triangle can be an isosceles triangle IF one of the sides has a different length than the rest and the angle measurement is different.