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Lesson Plan
EngageNY

Looking More Carefully at Parallel Lines

For Students 9th - 10th Standards
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...
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Lesson Plan
EngageNY

Review of the Assumptions (part 2)

For Students 9th - 10th Standards
Is the amount of information getting overwhelming for your geometry classes? Use this strategy as a way to organize information. The resource provides a handout of information studied in relation to triangle congruence. It includes a...
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Lesson Plan
Curated OER

Geometry, Measurement & Reasoning

For Teachers 9th - 11th
Students construct two-column proofs. In this geometry activity, students use deductive reasoning and geometric properties to justify given geometric statements. Students compare and contrast proofs.
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Lesson Plan
Curated OER

Paragraph Proofs

For Teachers 9th - 12th
Students explore the concept of paragraph proofs. In this paragraph proofs lesson, students make flow charts of the process of getting ready for school. Students convert the flow chart to a paragraph proof. Students use geometric...
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Worksheet
Curated OER

Indirect Euclidean Proofs

For Students 10th
In this Euclidean proofs activity, 10th graders solve 10 different problems that include completing indirect Euclidean proofs. First, they write a statement for each of the reasons listed on the sheet of proofs. Then, students solve the...
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Worksheet
Curated OER

Indirect Euclidean Proofs

For Students 7th - 8th
In this indirect Euclidean proof worksheet, students write statements supporting the reasons for a given proof. This one-page worksheet contains ten problems.
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Worksheet
Curated OER

Quiz: Beginning Congruent Triangle Proofs

For Students 10th - 11th
In this congruent triangle proof worksheet, students write theorems to prove the congruence of given triangles. This one-page worksheet contains three given polygons to prove congruence.
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Lesson Plan
Curated OER

The Truth About Triangles And Proofs

For Teachers 9th - 12th
Learners engage in a lesson that is about the classification of triangles and the mathematical proofs involved in working with them. They work on a variety of problems that are created by the teacher with the focus upon the importance of...
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Lesson Plan
EngageNY

Solve for Unknown Angles—Angles and Lines at a Point

For Teachers 9th - 10th Standards
How do you solve for an unknown angle? For this sixth installment of a 36-part series, young mathematicians use concepts learned in middle school geometry to set up and solve linear equations to find angle measures.
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Lesson Plan
EngageNY

Proving the Area of a Disk

For Teachers 9th - 10th Standards
Using a similar process from the first lesson in the series of finding area approximations, a measurement resource develops the proof of the area of a circle. The problem set contains a derivation of the proof of the circumference formula. 
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Lesson Plan
EngageNY

Properties of Parallelograms

For Teachers 9th - 10th Standards
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...
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Lesson Plan
EngageNY

Ptolemy's Theorem

For Teachers 9th - 12th Standards
Everyone's heard of Pythagoras, but who's Ptolemy? Learners test Ptolemy's Theorem using a specific cyclic quadrilateral and a ruler in the 22nd installment of a 23-part module. They then work through a proof of the theorem.
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Instructional Video15:58
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Flipped Math

Reasoning and Proof

For Students 9th - 12th
Make sure the conditions are right. Pupils watch a video introducing conditional statements and their related statements. Learners find out how to identify the hypothesis and conclusion as well as write the converse, inverse, and...
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Lesson Plan
Curated OER

Triangle's Interior Angles

For Teachers 7th - 9th Standards
Given a pair of parallel lines and a triangle in between, geometers prove that the sum of the interior angles is 180 degrees. This quick quest can be used as a pop quiz or exit ticket for your geometry class.
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Lesson Plan
Curated OER

Two Column Logic Proofs

For Teachers 8th - 10th
Students complete two column proofs. In this geometry lesson,students derive the reasons their answers are correct using logic. They write the proof step by step using two columns.
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Worksheet
Curated OER

Proofs with Triangles

For Students 9th - 10th
In this geometry learning exercise, student solve problems with triangles using proofs. They identify the solution based on SSS, SAS, ASA. There are 5 proofs tobe completed.
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Worksheet
Curated OER

Four Algebraic Proof Charts

For Students 8th - 10th
In this proof chart worksheet, learners are given an equation and asked to solve for the unknown and to justify the steps by filling in the proof using math properties.  The worksheet contains four problems presented as proof charts.
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Worksheet
Curated OER

The Premises of Geometry

For Students 9th - 10th
In this geometry worksheet, students solve for missing midpoints, segments and angles using algebraic equations. They use geometric properties to solve these equations. There are 32 questions on 7 different worksheets.
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Worksheet
Curated OER

SSS, SAS, ASA, and AAS Congruence

For Students 8th - 10th
Students will determine if triangles are congruent and state the appropriate congruence theorem. In this geometry lesson, students will determine what information is needed to determine if a pair of triangles are congruent using ASA,...
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Lesson Plan
Curated OER

Indirect Proof and Inequalities in One Triangle

For Teachers 10th
In this geometry worksheet, 10th graders order the sides and angles of a triangle and determine the range of the third side of a triangle given the lengths of two sides.  The one page worksheet contains sixteen questions.  Answers are...
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Lesson Plan
Curated OER

Coordinate Proofs

For Teachers 9th - 12th
Students explore the concept of coordinate proofs. In this coordinate proofs lesson plan, students write coordinate proofs using properties of distance, slope, and midpoint. Students discuss why it is sometimes beneficial to double the...
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Lesson Plan
EngageNY

Unknown Angle Proofs—Proofs of Known Facts

For Teachers 9th - 10th Standards
Lead the class in a Greek history activity 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...
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Lesson Plan
EngageNY

Analytic Proofs of Theorems Previously Proved by Synthetic Means

For Students 9th - 12th Standards
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....
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Lesson Plan
EngageNY

Mid-Module Assessment Task - Geometry (Module 1)

For Teachers 9th - 10th Standards
How do you prepare class members for the analytical thinking they will need in the real world? An assessment requires the higher order thinking they need to be successful. The module focuses on the concept of rigid transformations...

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