EngageNY
Properties of Parallelograms
Everyone knows that opposite sides of a parallelogram are congruent, but can you prove it? Challenge pupils to use triangle congruence to prove properties of quadrilaterals. Learners complete formal two-column proofs before moving on to...
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 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
Young scholars identify different properties of parallelograms. In this geometry lesson, students complete problems that proves the theorems and properties of parallelograms. They graph the different shapes on paper.
Curated OER
Application of Properties of Quadrilaterals in the Coordinate Plane
Students apply definitions and theorems to verify special quadrilaterals
using coordinate geometry. They apply the slope formula, the midpoint
formula, and the distance formula to justify that a given quadrilateral is a
parallelogram....
Key Curriculum Press
Properties of Special Parallelograms
Rhombuses, rectangles and squares are have special properties. In this lesson, young geometers investigate and make conjectures about diagonals, angles, and parallel lines of parallelograms.
EngageNY
How Do Dilations Map Segments?
Do you view proofs as an essential geometric skill? The resource builds on an understanding of dilations by proving the Dilation Theorem of Segments. Pupils learn to question and verify rather than make assumptions.
Illustrative Mathematics
Right Triangles Inscribed in Circles II
So many times the characteristics of triangles are presented as a vocabulary-type of activity, but in this activity they are key to unraveling a proof. A unique attack on proving that an inscribed angle that subtends a diameter must be a...
Virginia Department of Education
Properties of Quadrilaterals
What type of quadrilateral is that? Discover the difference between the types of quadrilaterals. Small groups investigate types of quadrilaterals using geometry software to find their properties. To keep track of the different...
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 practice...
Curated OER
Parallelism in Our Everyday World: Parallel Lines and Beyond
Students broaden their outlook on geometry in their everyday environment. They explore the properties of parallel lines and parallelograms and discover ways to prove the existence of parallel lines and discuss the concept of parallel lines.
Curated OER
Which Quadrilateral Is It?
Young scholars prove conjectures about geometric figures on the plane or in space using coordinate geometry. They develop fluency in operations with real numbers, vectors and matrices using mental computation or paper-and-pencil...
Curated OER
Investigating Area Using Tangrams
Tenth graders connect the history of geometry to problem solving. For this geometry lesson, 10th graders investigate polygons through hands on manipulatives and solve problems relating to parallelograms and triangles. They calculate the...
Curated OER
Applications of Properties of Quadrilaterals in the Coordinate Plane
Students explore the concept of quadrilaterals. In this quadrilaterals activity, students use the slope formula, midpoint formula, and distance formula to justify that a given quadrilateral is a parallelogram.
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
Ninth graders identify quadrilaterals and label the vertices of quadrilaterals. they justify their identification of the quadrilaterals. Students work in groups to identify and create quadrilaterals
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 three point...
Curated OER
Peter's String
Students are introduced to the math problem and consider how they could approach it. In pairs, students investigate Peter's conjecture in any way they see fit. They then share their answers with the class.