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Learning Goal

Part of: Prove geometric theorems1 of 3 cluster items

Prove theorems about lines

HSG.CO.C.9

**HSG.CO.C.9**: Prove theorems about lines and angles. Theorems include: vertical angles are congruent; when a transversal crosses parallel lines, alternate interior angles are congruent and corresponding angles are congruent; points on a perpendicular bisector of a line segment are exactly those equidistant from the segment's endpoints.

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HSG.CO.C.9: Prove theorems about lines and angles. Theorems include: vertical angles are congruent; when a transversal crosses parallel lines, alternate interior angles are congruent and corresponding angles are congruent; points on a perpendicular bisector of a line segment are exactly those equidistant from the segment's endpoints.

What you'll learn

  1. Prove that vertical angles are congruent using the properties of linear pairs and supplementary angles
  2. Prove that when a transversal crosses parallel lines, alternate interior angles are congruent
  3. Prove that when a transversal crosses parallel lines, corresponding angles are congruent
  4. Prove the Perpendicular Bisector Theorem: points on a perpendicular bisector of a segment are exactly those equidistant from the segment's endpoints
  5. Construct logical proofs using both two-column and paragraph formats, citing definitions, postulates, and previously established theorems as justifications

Slides

Interactive presentations perfect for visual learners • 2 slide decks

Slide Video

Watch narrated slides play like a video lesson • Narrated slide playback

Exercises

Practice problems to build fluency and understanding • 1 exercises