Khan Academy: High School Geometry
Khan Academy

Learn high school geometry for free—transformations, congruence, similarity, trigonometry, analytic geometry, and more.

GeoGebra: Moving in the Plane - IM 8.1.1
GeoGebra

“Moving in the Plane” from IM Grade 8 by Open Up Resources and Illustrative Mathematics.

GeoGebra: Making the Moves - IM 8.1.4
GeoGebra

“Making the Moves” from IM Grade 8 by Open Up Resources and Illustrative Mathematics.

GeoGebra: Naming the Moves - IM 8.1.2
GeoGebra

“Naming the Moves” from IM Grade 8 by Open Up Resources and Illustrative Mathematics.

GeoGebra: Coordinate Moves - IM 8.1.5
GeoGebra

“Coordinate Moves” from IM Grade 8 by Open Up Resources and Illustrative Mathematics.

GeoGebra: Grid Moves IM 8.1.3
GeoGebra

“Grid Moves” from IM Grade 8 by Open Up Resources and Illustrative Mathematics.

GeoGebra: What Is the Same? IM 8.1.11
GeoGebra

“What Is the Same?” from IM Grade 8 by Open Up Resources and Illustrative Mathematics.

GeoGebra: Congruent Polygons IM 8.1.12
GeoGebra

“Congruent Polygons” from IM Grade 8 by Open Up Resources and Illustrative Mathematics.

GeoGebra: Congruence IM 8.1.13
GeoGebra

“Congruence” from IM Grade 8 by Open Up Resources and Illustrative Mathematics.

Inside Mathematics: 9th & 10th Grade Math - Properties of Quadrilaterals
Inside Mathematics (The University of Texas at Austin, Charles A. Dana Center)

This lesson is about properties of quadrilaterals and learning to investigate, formulate, conjecture, justify, and ultimately prove mathematical theorems.