What is the purpose of a two-column proof in geometry?

To provide a structured way to present statements and their corresponding reasons to prove a geometric theorem.

In the video's proof, which congruence postulates were used to prove that segment AC is perpendicular to segment DB?

Side-Side-Side (SSS) and Side-Angle-Side (SAS)

In your own words, describe how the Side-Side-Side (SSS) postulate was applied in the video's proof. Be specific about which segments were used to establish congruence.

The SSS postulate was used to prove that triangle CDA is congruent to triangle CBA. This was done by showing that segment CD is congruent to segment CB, segment DA is congruent to segment BA, and segment CA is congruent to itself.

Geometric Proofs

9th GradeMath30 min

Learning Objective

I can write a two-column proof to prove geometric theorems.

Lesson Flow

Watch Video

12 min

Two column proof showing segments are perpendicular | Congruence | Geometry | Khan Academy

Khan Academy

Guided Notes

6 min

Key concepts students will learn:

•
A two-column proof includes a statement and a reason for the statement.
•
If three sides of two triangles are congruent, then the triangles are congruent by the side-side-side postulate.
•
If two triangles are congruent, then all of their corresponding angles are equivalent.

Practice

10 min

3 questions • Multiple choice & Short answer

Exit Ticket

5 min

“Given: AB ≅ CD, BC ≅ DA. Prove: ∠B ≅ ∠D using a two-column proof.”

Teacher Guide

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Answer keys for all questions
Differentiation strategies
Extension activities
Printable student handouts

Geometric Proofs

Learning Objective

Lesson Flow

Watch Video

Guided Notes

Practice

Exit Ticket

Teacher Guide

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