Is an equilateral triangle is sometimes, never or always an isosceles triangle?
It is always an isosceles triangle.
The definition of an isosceles triangle is that it was 2 congruent sides. The definition of an equilateral triangle is that all sides are congruent. That means that at least 2 sides of the equilateral triangle are congruent, therefore we can conclude that it is isosceles, as long as equilateral.