Education Development Center
Proof with Parallelogram Vertices
Geometric figures are perfect to use for proofs. Scholars prove conjectures about whether given points lie on a triangle and about midpoints. They use a provided dialogue among fictional learners to frame their responses.
Illustrative Mathematics
Points equidistant from two points in the plane
Young geometers apply their deductive reasoning skills and knowledge of proving triangles congruent in a task that asks them to prove if a point lies on the perpendicular bisector of a segment, then it is equidistant from the endpoints...
Curated OER
SAS Similarity Theorem
Students identify and use the similarity theorem. In this geometry instructional activity, students differentiate between congruent and similar triangles. They solve problems using the computer modifying shapes by dragging.
Illustrative Mathematics
Midpoints of the Sides of a Paralellogram
This task asks learners to prove that the segment joining the midpoints of two sides of a parallelogram is both congruent and parallel to an adjacent side of the parallelogram. The activity would be good to use in a discussion about how...
Curated OER
Proportional Parts
In this geometry instructional activity, students identify what makes triangles similar and congruent. They use SSS,SAS and AA to identify the correct ratio of each triangle. There are 15 questions.
Curated OER
Indirect Euclidean Proofs
In this indirect Euclidean proof worksheet, students write statements supporting the reasons for a given proof. This one-page worksheet contains ten problems.
Curated OER
Logical Relationship of Postulates & Theorems
In this postulates and theorems worksheet, students explore a concept map containing information about angles and sides, alternate interior angles, and diagonals of a parallelogram. They use the concept map to prove theorems dealing...
Curated OER
Investigating AAS
Students investigate the theorems of ASA, AAS, AAA and ASA. In this geometry lesson, students discuss the theorems of triangles and how it is used to solve for missing sides or angles. They review how two angles are formed by two rays...
Massachusetts Department of Education
Similarity through Transformations
Create the ultimate miniature golf course. The 93-page model curriculum unit from the Massachusetts Department of Elementary and Secondary Education contains nine lessons on understanding similarity in terms of both Euclidean geometry...
Curated OER
Angles and Similarity
High schoolers identify triangles as similar or congruent. In this geometry lesson, students drag triangles around on the navigator to see the effect of different angles on the shape of the triangle. They discuss angle similarity and...
Curated OER
Why Doesn't SSA Work?
Students investigate the relationship between angles and their sides. In this geometry lesson, students prove why SSA does not work as a true angle side relationship theorem.
Curated OER
Circle Proofs
For this circle proofs worksheet, 10th graders complete 4 different problems that include circle proofs. They respond to each of the questions that deal with circle proofs. Then, students read the given information and use the circle...
Curated OER
Proportional Similarities
Pupils model the geometric relationship with graphing. In this geometry lesson, students differentiate between parallel, perpendicular, similar and congruent shapes. They use properties of polygons to differentiate their shapes correctly.
Curated OER
Trapezoids
In this trapezoids worksheet, 10th graders solve 5 different problems related to trapezoids and applying the appropriate theorem. First, they define a trapezoid, including its bases, legs, and base angles. Then, students use the...
Curated OER
Math: Tangents
Young scholars discover how to recognize tangents and how to use their properties. They investigate and use the properties of angles, arcs, chords, tangents, and secants. Students use two tangents and the properties of similar...
Mathematics Vision Project
Circles: A Geometric Perspective
Circles are the foundation of many geometric concepts and extensions - a point that is thoroughly driven home in this extensive unit. Fundamental properties of circles are investigated (including sector area, angle measure, and...
Curated OER
Proofs Of The Pythagorean Theorem?
Even U.S. President James Garfield had his own proof of the Pythagorean Theorem! Pupils consider three different attempts at a geometric proof of the Pythagorean Theorem. They then select the best proof and write paragraphs detailing...
EngageNY
Tangent Segments
What's so special about tangents? Learners first explore how if a circle is tangent to both rays of an angle, then its center is on the angle bisector. They then complete a set of exercises designed to explore further properties and...
EngageNY
General Pyramids and Cones and Their Cross-Sections
Are pyramids and cones similar in definition to prisms and cylinders? By examining the definitions, pupils determine that pyramids and cones are subsets of general cones. Working in groups, they continue to investigate the relationships...
Curated OER
Tangrams
Young scholars construct tangram pieces. Then they make observations and explore patterns with the pieces.
Curated OER
Similar Polygons
In this similar polygons worksheet, 10th graders solve and complete 20 various types of problems. First, they solve each proportion. Then, students write a ratio expressing the slope of a line through each pair of points. In addition,...
Curated OER
Why do Stars Rise in the East?
In this stars rise in the east instructional activity, students use geometry to show how the Earth rotates from west to east and why celestial bodies appear to rise in the east and set in the west. Students draw a figure and label given...
Curated OER
Polygons All Around Us!
Students explore the concept of polygon properties. In this polygon properties lesson, students draw polygons with different numbers of sides such as pentagons, octagons, hexagons, etc. Students identify different geometric shapes in the...
Curated OER
Tangrams
Students construct the tangram pieces from a square paper by following directions to fold and cut. They make observations on the pieces formed and compare how they are related to each other. They explore patterns and shapes with the...