Curated OER
Co-exterior Angles Worksheet
In this geometry worksheet, 10th graders analyze angles created by a transversal. They identify co-exterior angles as they review theorems dealing with parallel lines. There are 6 questions with an answer key.
EngageNY
Unknown Angle Proofs—Proofs with Constructions
Provide your emerging mathematicians with the tools to learn as they incorporate auxiliary lines to solve unknown angle proofs in this continuing segment. They decipher information from a diagram to uncover the missing pieces and...
Curated OER
Light Bounce
Students solve problems involving triangles. In this geometry instructional activity, students apply properties of triangles to find the missing angles and sides. They identify angles of parallel lines cut by a transversal.
Curated OER
Angle Pairs
Students identify different angle pairs. In this geometry instructional activity, students identify the different angles of two parallel lines cut by a transversal. They identify the interior and exterior angles.
Curated OER
Angle Action 1,2 and 3
Students investigate angles through construction. In this geometry lesson, students use a protractor to identify the measurement of an angle. They identify angles cut by a transversal and two parallel lines.
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...
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 students to frame their responses.
Inside Mathematics
Circles in Triangles
Challenge the class with inscribed circles in triangles. The assessment task requests class members use their knowledge of circles and right triangles to prove two triangles are congruent. They go on to utilize their knowledge of...
Illustrative Mathematics
Is This a Parallelogram?
If both pairs of opposite sides of a quadrilateral are congruent, is the quadrilateral a parallelogram? This task asks learners to determine the answer and to support their answer with a proof. The resource includes a commentary for...
Curated OER
Geometric Lines: Parallel / Transversal / Perpendicular
Students in grade 7 and 8 work on outcomes related to spatial sense and geometric concepts, properties, and relationships. The lesson integrates technology and helps students be exposed to multimedia.
Curated OER
Side Splitter Triangles
Students investigate the side splitter theorem. In this geometry lesson plan, students estimate and solve problems dealing with ratios and proportions. They identify angles created by lines that are parallel.
West Contra Costa Unified School District
Investigating Similar Triangles
Let your use of the resource be in proportion to its usefulness. Pupils investigate similar triangles by measuring side lengths and considering given angle measures. The results of the investigation help develop generalizations about...
Virginia Department of Education
High School Mathematics Geometry Vocabulary Word Wall Cards
Having a good working knowledge of math vocabulary is especially important for geometry learners. Here are 119 pages worth of wonderfully constructed definitions, constructions, formulas, properties, theorems, and postulates. This is a...
EngageNY
Congruence, Proof, and Constructions
This amazingly extensive unit covers a wealth of geometric ground, ranging from constructions to angle properties, triangle theorems, rigid transformations, and fundamentals of formal proofs. Each of the almost-forty lessons is broken...
Mathematics Assessment Project
Identifying Similar Triangles
Math whizzes work with angle sums and exterior angles to figure out the measure of other angles. This particular publication provides comprehensive support in the form of an anticipatory activity, questions designed to prompt discussion,...
EngageNY
Similarity and the Angle Bisector Theorem
Identifying and verifying reproducible patterns in mathematics is an essential skill. Mathematicians identify the relationship of sides when an angle is bisected in a triangle. Once the pupils determine the relationship, they prove it to...
Curated OER
The Tipping Point
Students rewrite word problems and solve using math. In this word problem lesson, students gather data and observe the data. They relate this process to the scientific method and math. They review their data to be able to answer...
EngageNY
Informal Proof of AA Criterion for Similarity
What does it take to show two triangles are similar? The 11th segment in a series of 16 introduces the AA Criterion for Similarity. A discussion provides an informal proof of the theorem. Exercises and problems require scholars to apply...
Curated OER
Geometry: Lesson 8
Eighth graders engage in a lesson that is concerned with the finding of angles that are found in different two dimensional figures. They compare and contrast exterior and interior angles while also determining the unknown measures of...
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...
EngageNY
Congruence Criteria for Triangles—SAS
Looking for a different approach to triangle congruence criteria? Employ transformations to determine congruent triangles. Learners list the transformations required to map one triangle to the next. They learn to identify congruence if...
EngageNY
More About Similar Triangles
Determine whether two triangles are similar. The lesson presents opportunities for pupils to find the criterion needed to show that two triangles are similar. Scholars use the definition of similarity to find any missing side...
Curated OER
Constructing Midsegments of Triangles
Learners construct midsegments. In this geometry instructional activity, students make conjectures and apply properties of triangles to solve problems. They complete an activity on the computer.
Curated OER
Strongest Polygon
Learners define and identify shapes by name. In this geometry lesson plan, students construct, identify and compare polygons based on the number of sides. They classify each shape based on their angle sum theorem.