Definition

1. Noun:
   • A three-sided regular polygon: An "equilateral triangle" is a triangle in which all three sides are of equal length. Consequently, all three internal angles are also equal, each measuring 60 degrees.

Usage Examples

• Noun:
  • The logo was a simple blue equilateral triangle.
  • In geometry class, we learned to construct an equilateral triangle using only a compass and a straightedge.
  • All sides of an equilateral triangle are congruent.

Advanced Usage

• Mathematical Context: The term is used precisely in geometry and trigonometry. It is one of the three types of triangles classified by side lengths, the others being "isosceles" and "scalene."
  • The area of an equilateral triangle can be calculated if the length of one side is known.

Variants and Related Words

• Equilateral (adjective): Having all sides equal.
  • An equilateral polygon.
• Regular triangle (noun): A less common synonym for "equilateral triangle."
• Triangle (noun): The general class of polygons with three sides and three angles.

Synonyms

• Regular triangle: A triangle that is both equiangular and equilateral.

Related Concepts (Not Phrasal Verbs or Idioms)

• Altitude/Height: A perpendicular line segment from a vertex to the opposite side. In an equilateral triangle, all altitudes are of equal length.
• Centroid, Incenter, Circumcenter, Orthocenter: For an equilateral triangle, these four triangle centers coincide at the same point.

Noun

1. a three-sided regular polygon