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West Contra Costa Unified School District
The Parallelogram Law
Use your pupils' sense of curiosity to explore the Parallelogram Law. Here is an activity that outlines a complete lesson plan from beginning to end, allowing pupils to follow a conjecture through to the proof stage.
EngageNY
Analytic Proofs of Theorems Previously Proved by Synthetic Means
Prove theorems through an analysis. Learners find the midpoint of each side of a triangle, draw the medians, and find the centroid. They then examine the location of the centroid on each median discovering there is a 1:2 relationship....
Curated OER
Properties of Parallelograms
Students identify different properties of parallelograms. In this geometry activity, students complete problems that proves the theorems and properties of parallelograms. They graph the different shapes on paper.
Key Curriculum Press
Properties of Special Parallelograms
Rhombuses, rectangles and squares are have special properties. In this activity, young geometers investigate and make conjectures about diagonals, angles, and parallel lines of parallelograms.
EngageNY
Unknown Angle Proofs—Proofs of Known Facts
Lead the class in a Greek history lesson with a geometric twist. Pupils relate a short video about geometric properties to modern-day methods of solving for unknown angles. They discuss parallel line theorems and complete...
Curated OER
Investigating Area Using Tangrams
Tenth graders connect the history of geometry to problem solving. In this geometry instructional activity, 10th graders investigate polygons through hands on manipulatives and solve problems relating to parallelograms and triangles. They...
Illustrative Mathematics
What is a Trapezoid? (Part 1)
Challenge your class to construct a definition for trapezoids. Looking at four examples and four non-examples, students individually create definitions and use them to classify an unknown shape. Allow for small group and whole-class...
EngageNY
Special Lines in Triangles (part 2)
Medians, midsegments, altitudes, oh my! Pupils study the properties of the median of a triangle, initially examining a proof utilizing midsegments to determine the length ratio of a median. They then use the information to find missing...
Curated OER
Quadrilateral Explorations-Grade Nine
Ninth graders investigate quadrilaterals. In this geometry lesson, 9th graders examine and classify quadrilaterals using the slope, midpoint and distance formulas. Additionally, students create various quadrilaterals given...