Properties of Triangles and Quadrilaterals — Classroom Resources

Open with Varignon’s Theorem — Midpoints of Any Quadrilateral Form a Parallelogram. Ask students what they notice and what question the resource raises before introducing the formal idea.

Let students explore Three Medians, Six Equal Areas, then ask them to describe the pattern, argument, or representation in their own words.

Let students explore Connect the Midpoints — Exactly Half, then ask them to describe the pattern, argument, or representation in their own words.

Let students explore Viviani’s Theorem — Three Distances Always Sum to the Height, then ask them to describe the pattern, argument, or representation in their own words.

Use Wherever the Point Lands — Opposite Triangles Match as an extension or assignment that connects the lesson to a broader mathematical story.

Use The Birth of Greek Geometry as an extension or assignment that connects the lesson to a broader mathematical story.

Use The River of Euclidean Geometry as an extension or assignment that connects the lesson to a broader mathematical story.