
Public learning track
Triangle Theorems and Deductive Properties
9th Grade · Math · Open Global Math
8 lessons
Goal
Prove fundamental triangle theorems including angle sums, inequalities, medians, centroids, and mid-segments.
Featured Diagrams
Triangle Angle Sum and Exterior Angle Theorems
8 lessons
0 of 8 done
- 1Triangle Angle Sum and Exterior Angle TheoremsUp nextStart
- 2Exterior Angle Theorem for TrianglesPremiumNot started yet
- 3Proving the Triangle Inequality TheoremNot started yet
- 4Angle-Side Relationships and the Hinge TheoremNot started yet
- 5Classifying Acute, Right, and Obtuse Triangles Using Side LengthsNot started yet
- 6The Triangle Mid-Segment Theorem and ProofNot started yet
- 7Medians and the Centroid TheoremNot started yet
- 8Concurrency of Altitudes, Perpendicular Bisectors, and Angle BisectorsNot started yet
Curriculum Framework
9th Grade · Math · Open Global Math
1
7 lessons
Geometric Reasoning, Axiomatic Systems, and Proof Methods
Understand the logical architecture of geometry and construct rigorous direct proofs, indirect proofs, and counterexamples.
2
13 lessons
Lines, Angles, and Geometric Constructions
Prove angle relationships involving intersecting and parallel lines and master classic Euclidean compass-and-straightedge constructions.
3
8 lessons
Triangle Theorems and Deductive Properties
Prove fundamental triangle theorems including angle sums, inequalities, medians, centroids, and mid-segments.
4
8 lessons
Triangle Congruence Criteria and Synthetic Proofs
Establish triangle congruence criteria (SAS, ASA, SSS, AAS, HL) and construct rigorous geometric proofs of triangle properties.
5
7 lessons
Properties and Proofs of Quadrilaterals and Polygons
Prove classification properties of special quadrilaterals, derive polygon angle sum formulas, and analyze tessellation conditions.
6
9 lessons
Similarity, Proportions, and Dilations
Prove and apply triangle similarity criteria, Thales' Theorem, area scaling laws, and explore the Golden Ratio.
7
7 lessons
Circle Theorems: Chords, Angles, and Cyclic Quadrilaterals
Prove circle theorems involving chords, central and inscribed angles, angles in the same segment, and cyclic quadrilaterals.
8
7 lessons
Tangents, Secants, and Circle Power Theorems
Prove tangent theorems, alternate segment theorem, power of a point, and execute circle tangent constructions.
9
5 lessons
Transformations, Symmetries, and Dilations in the Plane
Apply rigid motions, homothety/dilations, analyze rotational and reflectional symmetries, and calculate coordinate mappings.
10
8 lessons
Coordinate Geometry, Bearings, and Spatial Representations
Calculate coordinate distances, midpoints, slopes, navigate using three-figure bearings, and interpret 3D orthographic views and nets.