Curated OER
Quilt Patch Proof
Students construct a convincing argument that the same amount of fabric is needed for each color of quilt being made in a specific design. They justify the relationship between vertical angles and the sum of the interior angles. Students
Texas Instruments
Texas Instruments: Investigating the Triangle Inequality
One property of a triangle is that the sum of the lengths of any two sides must be greater than the length of the third side. [Requires Adobe Reader.]
Mathigon
Mathigon: Geometry: Angles and Polygons: Drawing Triangles
This lesson focuses on the Triangle Inequality, when the sum of the lengths of any two sides of a triangle is greater than the length of the third. When this happens, the three sides cannot form a triangle.
Khan Academy
Khan Academy: Constructing Triangles
Given the lengths of two sides of a triangle, what can we say about the third side? Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.