What is an equilateral triangle?

What is an equilateral triangle?

• A. A triangle with three equal sides.
• B. A triangle with two equal sides.
• C. A polygon having four sides.
• D. A triangle with all angles acute.

Answer: (A)

An equilateral triangle is defined by having three equal sides. When all three sides are the same length, the angles adjust so each interior angle is the same, specifically 60 degrees in Euclidean geometry. The other descriptions point to different shapes or types: two equal sides is an isosceles triangle, four sides makes a quadrilateral, and all angles acute describes an acute-angled triangle (which isn’t how an equilateral is defined, even though its angles are acute). So the best description is a triangle with three equal sides.

An equilateral triangle is defined by having three equal sides. When all three sides are the same length, the angles adjust so each interior angle is the same, specifically 60 degrees in Euclidean geometry. The other descriptions point to different shapes or types: two equal sides is an isosceles triangle, four sides makes a quadrilateral, and all angles acute describes an acute-angled triangle (which isn’t how an equilateral is defined, even though its angles are acute). So the best description is a triangle with three equal sides.