Definition

Noun: - Vertical angle: Either of the two equal and opposite angles formed by the intersection of two straight lines. These angles are directly across from each other at the intersection point (vertex).

Usage

• The term "vertical angle" is a specific geometric term. It is always used in the context of intersecting lines and their angles.
• It is typically used in its plural form, "vertical angles," as the concept always involves a pair of angles.
• Example: "When two lines intersect, they form two pairs of vertical angles."

Examples

• Noun:
  • In the diagram, angle A and angle C are vertical angles.
  • A key property of vertical angles is that they are always congruent (equal in measure).
  • The theorem states that vertical angles have equal measures.

Advanced Usage

• "Vertical angles theorem": A fundamental theorem in geometry which states that vertical angles are congruent.
  • The proof relied on the vertical angles theorem.

Variants and Related Words

• Adjacent angles: Angles that share a common vertex and side but do not overlap. These are often discussed alongside vertical angles.
• Congruent angles: Angles that have the exact same measure. Vertical angles are a primary example.
• Intersecting lines: Lines that cross at a point. This is the necessary condition for vertical angles to exist.

Synonyms

• Opposite angles: This is a direct synonym, commonly used in geometry to refer to vertical angles.

Related Concepts (Not Phrasal Verbs or Idioms)

• Linear pair: A pair of adjacent angles whose non-common sides are opposite rays. The angles in a linear pair are supplementary (their measures add to 180 degrees), which is a related but distinct concept from vertical angles.

Noun

1. either of two equal and opposite angles formed by the intersection of two straight lines