Foundation
Vocabulary, marked diagrams, guided constructions, and reduced-complexity practice.
Open FoundationUnit 03 · Weeks 6, 7, 8
Triangle Congruence & Proof
How can limited measurements prove that triangles and their corresponding parts must agree?
Lesson sequence
7 visual, printable lessons
Lesson 01
Triangle Classification & Angle Relationships
Classify by sides and angles, use the triangle angle sum, and connect exterior angles to remote interior angles.
Lesson 02SSS and SAS Congruence
Identify sufficient evidence for triangle congruence and organize theorem-based proofs about corresponding parts and centers.
Lesson 03ASA, AAS and HL Congruence
Identify sufficient evidence for triangle congruence and organize theorem-based proofs about corresponding parts and centers.
Lesson 04CPCTC and Multi-Step Triangle Proofs
Use proven triangle congruence to justify new side and angle relationships in multi-step arguments.
Lesson 05Isosceles and Equilateral Triangle Theorems
Identify sufficient evidence for triangle congruence and organize theorem-based proofs about corresponding parts and centers.
Lesson 06Triangle Inequality & Feasible Construction
Test feasible side lengths and determine the range of a missing side before attempting construction.
Lesson 07Perpendicular Bisectors, Angle Bisectors & Centers
Construct and compare circumcenter, incenter, centroid, and orthocenter locations.
Core
Complete grade-level reasoning, calculation, proof, and printable evidence.
Open CoreExtended
Generalization, proof revision, optimization, design, and transfer.
Open Extended