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Interactive
Scholastic

Study Jams! Congruent Figures

For Students 4th - 7th Standards
There is more to congruency than just looking similar. Learn the difference and calculate the matching angles and sides to prove the congruence between figures. Lesson has step-by-step slides and follows with an assessment. 
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Activity
Illustrative Mathematics

Reflections and Isosceles Triangles

For Teachers 9th - 11th Standards
Geometers explore symmetries of isosceles triangles by using rigid transformations of the plane. They complete four tasks, including congruence proofs, which illustrate the relationship between congruence and rigid transformations. The...
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Lesson Plan
Curated OER

Proportional Similarities

For Teachers 8th - 10th
Students model the geometric relationship with graphing. For this geometry lesson, students differentiate between parallel, perpendicular, similar and congruent shapes. They use properties of polygons to differentiate their shapes...
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Lesson Plan
Curated OER

Why can't We Use SSA to Prove Triangles Congruent?

For Teachers 9th - 10th
Students investigate triangles and congruences. In this geometry instructional activity, students differentiate between inductive and deductive reasoning. They differentiate between similar and congruent triangles.
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Lesson Plan
Curated OER

CSI Investigation of Congruence and Similarity

For Teachers 9th - 12th
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.
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Worksheet
Curated OER

Proofs

For Students 10th
In this proofs worksheet, 10th graders solve and graph 8 different equations. First, they prove that each triangle is either congruent or similar. Then, students use the concept of corresponding parts of congruent triangles to solve each...
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Lesson Plan
Mathematics Assessment Project

Evaluating Statements About Length and Area

For Teachers 9th - 12th Standards
Class members complete an assessment task by identifying whether statements about triangles and quadrilaterals are always true, sometimes true, or never true. They then participate in a sorting activity with the same objective.
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Interactive
CK-12 Foundation

Unit Circle: Medieval Castle Defense

For Students 10th - 12th Standards
Who needs a plan — let trigonometry protect you! Pupils determine the angle of an approaching enemy to a village wall. The scholars determine the exact value of trigonometric functions for the angle. Class members use trigonometry to...
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Lesson Plan
EngageNY

General Pyramids and Cones and Their Cross-Sections

For Teachers 9th - 10th Standards
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...
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Lesson Plan
Key Curriculum Press

Triangle Inequalities

For Teachers 8th - 11th Standards
Properties about triangles are explored in this activity. Geometers make conjectures about the length of a triangle's sides, the length of the angles in relation to the length of the sides, and the measure of the exterior angles of a...
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Interactive
Curated OER

Proportional Parts

For Students 9th - 10th
In this geometry worksheet, 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.
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Lesson Plan
Curated OER

Gougu Rule or Pythagoras' Theorem

For Teachers 5th
Fifth graders explore Pythagoras' Theorem. They examine the pattern linking the length of the hypotenuse of a right angled triangle and the length of the other two sides. Students find an unknown side in right angled triangles.
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Lesson Plan1:00
Mathematics Assessment Project

Modeling Motion: Rolling Cups

For Students 9th - 12th Standards
Connect the size of a rolling cup to the size of circle it makes. Pupils view videos of cups of different sizes rolling in a circle. Using the videos and additional data, they attempt to determine a relationship between cup measurements...
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Lesson Plan
Curated OER

The Pythagorean Theorem Lesson 2

For Teachers 8th - 12th
Learners discuss and review examples of the Pythagorean Theorem using a GSP, Geometer's Sketchpad, activity.
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Lesson Plan
Curated OER

Studying Special Segments in Triangles

For Teachers 8th - 10th
Learners investigate special segments in triangles. In this geometry instructional activity, students graph, compare, estimate and predict findings based on their data. They differentiate between similarity and congruence of triangles.
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Lesson Plan
EngageNY

There is Only One Line Passing Through a Given Point with a Given Slope

For Teachers 8th Standards
Prove that an equation in slope-intercept form names only one line. At the beginning, the teacher leads the class through a proof that there is only one line passing through a given point with a given slope using contradiction. The 19th...
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Lesson Plan
EngageNY

Law of Cosines

For Teachers 11th - 12th Standards
Build upon the Pythagorean Theorem with the Law of Cosines. The 10th part of a 16-part series introduces the Law of Cosines. Class members use the the geometric representation of the Pythagorean Theorem to develop a proof of the Law of...
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Worksheet
Curated OER

Chapter 4.5 Geometry Practice Problems

For Students 10th - 11th
In this geometry practice problems worksheet, students write geometric proofs to prove the validity of given circumstances. Students prove parallel lines, perpendicular lines, and similar angles. This four-page worksheet contains eight...
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Lesson Plan
Curated OER

Congruence with Robot Gobot

For Teachers 8th - 10th
Students identify the properties of solids and polygons. In this geometry lesson, students identify the different measurements of a triangle. They use congruence parts and theorem to prove their answer.
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Lesson Plan
Alabama Learning Exchange

"I Saw the Sine"

For Teachers 9th - 12th Standards
Discover trigonometric ratios that complement each other. Using two videos, the lesson introduces the trigonometric ratios. The class discovers the relationship between the sine and cosine of complementary angles.
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Activity
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Illustrative Mathematics

Midpoints of the Sides of a Paralellogram

For Teachers 9th - 12th Standards
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...
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Lesson Plan
Curated OER

Math: Tangents

For Teachers 9th - 10th
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...
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Worksheet
Curated OER

Transformations and Congruence

For Students 10th
In this transformations and congruence learning exercise, 10th graders solve and complete 5 different types of problems. First, they calculate the length of a line giving their answer in 3 significant figures. Then, students prove that...
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Lesson Plan
Curated OER

Why Doesn't SSA Work?

For Teachers 10th - 11th
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.

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