What is an equilateral triangle?

What is an equilateral triangle?

• A. ONE side length 2.
• B. THREE sides same length, THREE angles equal measure 60 degrees.
• C. All three angles 90 degrees.
• D. Two sides same length, two angles equal.

Answer: (B)

An equilateral triangle has all three sides the same length and all three interior angles equal. In any triangle, the angles add up to 180 degrees, so if all three are equal, each angle must be 60 degrees. That combination—three equal sides and three 60-degree angles—defines an equilateral triangle. The description given matches this exactly: three sides of equal length and three angles measuring 60 degrees. The other options don’t fit because one side length alone doesn’t guarantee all sides are equal, a 90-degree angle describes a right triangle, and two equal sides with two equal angles describes an isosceles triangle, not one where all three sides and all three angles are equal.

An equilateral triangle has all three sides the same length and all three interior angles equal. In any triangle, the angles add up to 180 degrees, so if all three are equal, each angle must be 60 degrees. That combination—three equal sides and three 60-degree angles—defines an equilateral triangle. The description given matches this exactly: three sides of equal length and three angles measuring 60 degrees. The other options don’t fit because one side length alone doesn’t guarantee all sides are equal, a 90-degree angle describes a right triangle, and two equal sides with two equal angles describes an isosceles triangle, not one where all three sides and all three angles are equal.