All equilateral triangles are also isosceles triangles?

True or False, depending on your definition of isosceles triangles!

Actually, whether your answer is true or false depends upon your definition of an isosceles triangle. Some mathematicians define an isosceles triangle as one with at least two sides, while others define an isosceles triangle as one with exactly two sides. The latter definition is the more generally accepted one. Since an equilateral triangle has three, not exactly two congruent sides, people using the second definition of isosceles triangles would say that the statement is false, not true.

False because an equilateral triangle has 3 equal sides whereas an isosceles triangle has only 2 equal sides