Angles, Parallel Lines & Transversals

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Last updated: 8/16/2025

Key Concepts:

  • Vertical Angles – When two lines intersect, the opposite (non-adjacent) angles are equal.
  • Supplementary Angles – Two angles whose sum is (180°).
  • Complementary Angles – Two angles whose sum is (90°).
  • Adjacent Angles – Two angles that share a common side and vertex.
  • Corresponding Angles (angles in the same relative positions when two lines are intersected by a transversal) are equal if and only if the two lines are parallel.
  • Alternate Interior Angles (interior angles on opposite sides of the transversal) are equal if and only if the two lines are parallel.
  • Same-Side Interior Angles (interior angles on the same side of a transversal) add up to (180°) if and only if the two lines are parallel.

Skills Covered:

  • Identifying different types of angles in geometric figures.
  • Using properties of angles to find unknown angles.
  • Applying transversal properties to solve for unknown variables in parallel line diagrams.

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