Definition

Noun: A triangle that has two sides of equal length. The angles opposite these equal sides are also equal to each other.

Usage

The term "isosceles triangle" is used specifically in geometry to classify a triangle based on its side lengths. It is a precise mathematical term. - An isosceles triangle can be identified by its two congruent sides. - The roof was designed in the shape of an isosceles triangle.

Examples

Advanced Usage

• "Isosceles triangle theorem": A theorem stating that if two sides of a triangle are congruent, then the angles opposite those sides are congruent.
  • The proof relied on the isosceles triangle theorem.
• "Isosceles right triangle": A specific type of isosceles triangle where the two equal sides form the right angle. It is also a 45-45-90 triangle.
  • The hypotenuse of an isosceles right triangle is √2 times the length of a leg.

Variants and Related Words

• Isosceles (adjective): Describing a geometric figure, typically a triangle, with two equal sides.
  • The polygon was an isosceles trapezoid.
• Equilateral triangle (noun): A triangle with all three sides equal.
• Scalene triangle (noun): A triangle with all three sides of different lengths.

Synonyms

• None that are exact. The term is a specific geometric classification. Descriptive phrases like "triangle with two equal sides" serve as explanations, not synonyms.

Related Phrases

• Base of an isosceles triangle: The side that is not one of the two equal sides.
  • The altitude was drawn to the base of the isosceles triangle.
• Legs of an isosceles triangle: The two equal sides.
  • The legs of the isosceles triangle were each 5 cm long.

Noun

1. a triangle with two equal sides