Unit 5 · Triangle Congruence and ProofProof-based

5.8Triangle Congruence Proofs

Quick Answer

A triangle congruence proof: (1) mark the diagram, (2) list what is given, (3) identify which shortcut applies, (4) write statements and reasons in two-column format, (5) state the congruence conclusion.

Essential Question

How do we write a complete, well-organized two-column proof that establishes triangle congruence?

Learning Goals

  • 1Plan a triangle congruence proof by analyzing the diagram.
  • 2Write complete two-column proofs using all five shortcuts.
  • 3Include CPCTC when needed to prove additional parts.
  • 4Identify and use implied information (Reflexive Property, vertical angles, parallel lines).

Key Vocabulary

Proof plan

A strategy for organizing a proof before writing it formally.

Implied information

Facts that can be concluded from a diagram without being explicitly stated (e.g., shared sides, vertical angles).

Full lesson content coming soon

Worked examples, guided practice problems, a workbook, quiz, and downloadable PDF resources will be added to this lesson in Phase 2. The learning goals and vocabulary above reflect the complete lesson scope.