HSG-CO.C.10

Prove theorems about triangles. Theorems include: measures of interior angles of a triangle sum to 180 degrees; base angles of isosceles triangles are congruent; the segment joining midpoints of two sides of a triangle is parallel to the third side and half the length; the medians of a triangle meet at a point.

 
48 Lesson(s)
   

Tremendous Triangles Projects

Geometry » Unit: Tremendous Triangles
Geometry » Unit: Tremendous Triangles
Stephanie Conklin
Saratoga Springs, NY
Environment: Suburban
 
Big Idea:

It's students' time to shine! Students develop their own problem and then shoot a video to explain how to prove their triangles congruent.

 
Favorites (9)
 
Resources (12)
 
Reflections (1)
video shoot image tremendous triangle project
   

The Rope Stretcher

Geometry » Unit: Area Relationships
Geometry » Unit: Area Relationships
Tom Chandler
Ault, CO
Environment: Rural
 
Big Idea:

Students apply the Pythagorean Theorem and criteria for triangle congruence in a proof...and learn how the ancient pyramids of Egypt were laid out.

 
Favorites (10)
 
Resources (26)
theropestretcher image
   

Mid-Segment Maylay

Geometry » Unit: Three Triangle Topics
Geometry » Unit: Three Triangle Topics
Stephanie Conklin
Saratoga Springs, NY
Environment: Suburban
 
Big Idea:

Students will construct mid-segments in triangles and discover key properties of mid-segments within triangles.

 
Favorites (8)
 
Resources (19)
 
Reflections (2)
midpoint maylay image
   

Group Assessment: Triangle Congruence and Proof

Geometry » Unit: Discovering and Proving Triangle Properties
Geometry » Unit: Discovering and Proving Triangle Properties
Jessica Uy
Sunnyvale, CA
Environment: Suburban
 
Big Idea:

By analyzing other students' work, students will gain an understanding of the features of high-quality proofs while developing habits of mind.

 
Favorites (8)
 
Resources (11)
 
Reflections (1)
group test lesson image resized
   

What Are We Gonna Learn?

Geometry » Unit: Area Relationships
Geometry » Unit: Area Relationships
Tom Chandler
Ault, CO
Environment: Rural
 
Big Idea:

We begin the unit with a puzzle--and students learn why so many proofs of a familiar theorem are based on transforming areas.

 
Favorites (3)
 
Resources (24)
whatarewegonnalearn image
   

Left-Over Squares

Geometry » Unit: Area Relationships
Geometry » Unit: Area Relationships
Tom Chandler
Ault, CO
Environment: Rural
 
Big Idea:

Students analyze a transformation proof for rigor and learn that a famous theorem means more than "a squared plus b squared equals c squared".

 
Resources (29)
leftoversquares image
   

Shifty Shears

Geometry » Unit: Area Relationships
Geometry » Unit: Area Relationships
Tom Chandler
Ault, CO
Environment: Rural
 
Big Idea:

We use Cavalieri's Principle to analyze racing yacht sails, the face of a deck of cards, and shears...which are used in yet another transformation proof.

 
Resources (26)
shiftyshears image
   

Triangle Congruence and CPCTC Practice

Geometry » Unit: Discovering and Proving Triangle Properties
Geometry » Unit: Discovering and Proving Triangle Properties
Jessica Uy
Sunnyvale, CA
Environment: Suburban
 
Big Idea:

Through a kinesthetic menu activity, students will be able to use congruent triangles to write proofs about special triangles and quadrilaterals.

 
Favorites (11)
 
Resources (11)
playground equipment triangles
   

Discovering and Proving Triangle Properties Unit Assessment

Geometry » Unit: Discovering and Proving Triangle Properties
Geometry » Unit: Discovering and Proving Triangle Properties
Jessica Uy
Sunnyvale, CA
Environment: Suburban
 
Big Idea:

In this unit assessment, students will demonstrate their understanding of triangle congruence and proof in a series of multiple choice, open-ended, and proof-based questions.

 
Favorites (2)
 
Resources (5)
test sample proof
   

Triangle Inequality Theorem Investigation

Geometry » Unit: Proofs about Triangles
Geometry » Unit: Proofs about Triangles
Marisa Laks
New York, NY
Environment: Urban
 
Big Idea:

Students investigate and make conclusions about sets of potential sides of triangles in order to discover the triangle inequality theorem.

 
Favorites (13)
 
Resources (13)
 
Reflections (1)
triangle inequality image
   

CPCTC

Geometry » Unit: Proofs about Triangles
Geometry » Unit: Proofs about Triangles
Marisa Laks
New York, NY
Environment: Urban
 
Big Idea:

Students will use their knowledge of the ASA, SAS and SSS postulates to prove corresponding parts of congruent triangles are congruent.

 
Favorites (4)
 
Resources (14)
cpctc image
   

Angle-Side-Angle

Geometry » Unit: Proofs about Triangles
Geometry » Unit: Proofs about Triangles
Marisa Laks
New York, NY
Environment: Urban
 
Big Idea:

Students will write formal proofs showing how triangles are congruent when two corresponding angles and the included side are congruent.

 
Favorites (3)
 
Resources (18)
 
Reflections (1)
asa image
   

Angles of a Triangle

Geometry » Unit: Parallel Lines
Geometry » Unit: Parallel Lines
Beth Menzie
Amsterdam, NY
Environment: Urban
 
Big Idea:

Students learn about the different types of triangles, the relationships between the interior and exterior angles of a triangle, and apply their knowledge to numerical problems and constructions.

 
Favorites (17)
 
Resources (23)
 
Reflections (1)
image triangles
   

Time for Triangles

Geometry » Unit: Tremendous Triangles
Geometry » Unit: Tremendous Triangles
Stephanie Conklin
Saratoga Springs, NY
Environment: Suburban
 
Big Idea:

Students will measure, cut and measure again to learn and prove key properties of triangles

 
Favorites (3)
 
Resources (28)
 
Reflections (2)
tri image time for triangles
   

Relationships between Angles and Sides of a Triangle

Geometry » Unit: Proofs about Triangles
Geometry » Unit: Proofs about Triangles
Marisa Laks
New York, NY
Environment: Urban
 
Big Idea:

This lesson gives students the opportunity to discover the relationship between the sides and angles of a triangle through a hands-on activity.

 
Resources (16)
 
Reflections (1)
relationships between angles and sides of a triangle image
Common Core Math
 
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