Curated OER
Crystals: Geometry and Groups
Students discuss the importance of examining crystals and experiment growing them. In groups, they complete a project in which they use groups in geometry just like crystallographers. They practice solving the groups and proofs and...
EngageNY
Looking More Carefully at Parallel Lines
Can you prove it? Making assumptions in geometry is commonplace. This resource requires mathematicians to prove the parallel line postulate through constructions. Learners construct parallel lines with a 180-degree rotation and then...
Curated OER
Developing Formulas for Triangles and Quadrilaterals
In this geometry worksheet, 10th graders determine the area of triangles, parallelograms, trapezoids, kites, and rhombuses. The one page worksheet contains eleven problems. Answers are included.
Virginia Department of Education
Similar Triangles
Pupils work in pairs to investigate what it takes to prove that two triangles are similar. They work through various shortcuts to find which are enough to show a similarity relationship between the triangles. Small groups work with the...
EngageNY
Solve for Unknown Angles—Transversals
Lead your class on an exciting journey through the world of math as they review geometry facts and solve for unknown angles. They learn how to use auxiliary lines and congruent angles to correctly complete each practice problem...
EngageNY
Triangle Congruency Proofs (part 1)
Can they put it all together? Ninth graders apply what they know about proofs and triangle congruence to complete these proofs. These proofs go beyond the basic triangle congruence proofs and use various properties, theorems, and...
Mathematics Vision Project
Geometric Figures
Logical thinking is at the forefront of this jam-packed lesson, with young mathematicians not only investigating geometric concepts but also how they "know what they know". Through each activity and worksheet, learners wrestle with...
Curated OER
NON-EUCLIDEAN GEOMETRY.
Students study relationships between angles, side lengths, perimeters, areas and volumes of similar objects. In this lesson students also create and critique inductive and deductive arguments concerning congruency, similarity and the...
CK-12 Foundation
Distance Between Two Points: Segment Addition
Examine the segment addition postulate through an online simulation activity. An interactive lesson allows scholars to manipulate points and watch as the lengths of segments change. Through their study, they are able to apply the Segment...
CK-12 Foundation
Angle Measurement: Adding Angles
Build angles from angles. Using the Angle Addition Postulate, learners find the measures of unknown angles. The interactive simulation shows a visual representation of the postulate and allows individuals to manipulate the angles and...
Curated OER
Congruent Triangles
Tenth graders explore congruent triangles. In this geometry lesson, 10th graders investigate the conditions necessary to prove two triangles are congruent by SSS, ASA, AAS, or SAS.
Curated OER
Triangle Inequality Theorems Investigation
Young scholars estimate and measure triangles. In this geometry lesson, students identify the relationship between three sides and a triangle. They use the inequality theorem to decide if a triangle will be formed or not.
Illustrative Mathematics
Joining Two Midpoints of Sides of a Triangle
Without ever using the actual term, this exercise has the learner develop the key properties of the midsegment of a triangle. This task leads the class to discover a proof of similar triangles using the properties of parallel...
Curated OER
The Right Angle
In this geometry worksheet, 10th graders determine the answer to a vocabulary questions and then follow the give rules to place the answer in the appropriate place on the crossword grid. The one page worksheet contains 18...
Curated OER
Geometry Practice: G.G. 28 #2: Triangle Congruence
In this triangle congruence worksheet, students use SSS, ASA, AAS and HL to determine the congruence of triangles. They identify the theorem that proves congruence. This three-page worksheet contains 4 multi-step...
Curated OER
Congruent Triangles
Young scholars explore the concept of congruent triangles. In this congruent triangles lesson plan, students use Cabri Jr. to construct two congruent triangles using circles. Young scholars determine if the two triangles are...
Curated OER
Angles and Arcs
Students discuss the sum of central angles and use string to create them on circles. They find the measure and length of both minor and major arcs.
Students give examples of concentric, similar, and congruent circles and congruent arcs.
Curated OER
Similarity and Congruence
Students determine that two figures are similar or congruent by
investigating figures that are similar and figures that are congruent. They prove that two figures are similar or congruent by using definitions,
postulates, and theorems.
Curated OER
Preparation and Transition to Two-Column Proofs
Students investigate proofs used to solve geometric problems. In this geometry lesson plan, students read about the history behind early geometry and learn how to write proofs correctly using two columns. The define terminology valuable...
Texas Instruments
Trisecting a Square
High Schoolers investigate the question of whether or not the area of square can be trisected. In this activity, they use geometry software to answer the questions and determine what conditions are necessary to the three regions to by...
Curated OER
Why can't We Use SSA to Prove Triangles Congruent?
Students investigate triangles and congruences. For this geometry lesson, students differentiate between inductive and deductive reasoning. They differentiate between similar and congruent triangles.
Math Worksheets Center
Congruent Triangle Proofs Quiz
A congruent triangles quiz challenges teenage mathematicians to complete a pair of geometric proofs. Each problem includes a picture of the triangles in question, a given set of information, and the five steps needed to finish the proof....
Curated OER
CSI Investigation of Congruence and Similarity
Students differentiate between similarity and congruence using polygons. In this geometry lesson, students label triangles based on their properties. They find missing sides and angles using the interior sum theorem.
Curated OER
The Flat Earth
Students differentiate between different planes. For this geometry lesson, students differentiate between a plane and a sphere. They discuss the Great Circle, Geodesic and Lune as it relates to the earth.