A triangle with equal-length sides is called an equilateral triangle. Each angle in an equilateral triangle is 60o, so the angles are all the same size. An equilateral triangle has the following traits: All three sides of the triangle are the same length. Each angle is 60o, and they are all the same. The three sides of an equilateral triangle are all the same length. In an equilateral triangle, the middle point, the line that cuts the angle in half, and the length of each side are all the same.