8.G.A.5

Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles. For example, arrange three copies of the same triangle so that the sum of the three angles appears to form a line, and give an argument in terms of transversals why this is so.

 
40 Lesson(s)
   

PTA (Parallel Lines, Transversals and Angles)

Geometry » Unit: Line-sanity!
Geometry » Unit: Line-sanity!
Stephanie Conklin
Saratoga Springs, NY
Environment: Suburban
 
Big Idea:

Students will draw and measure to discover relationships of angles formed by parallel lines cut by a transversal.

 
Favorites (19)
 
Resources (20)
 
Reflections (1)
parallel wires pta lesson
   

My Little Transversal: A multi-day project lesson

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
Shaun Errichiello
New York, NY
Environment: Urban
 
Big Idea:

Looking for a direct or an abstract connection to a concept can bring math content to life.

 
Favorites (12)
 
Resources (14)
 
Reflections (2)
screen shot 2014 02 09 at 3 18 16 pm
   

Super Practice with Angles and Algebra

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
Shaun Errichiello
New York, NY
Environment: Urban
 
Big Idea:

Students can only master a topic if they are given the opportunities needed to practice the topic.

 
Favorites (9)
 
Resources (33)
 
Reflections (1)
screen shot 2014 02 09 at 12 10 46 am
   

Angles and Parallel Lines (Day 2 of 2)

8th Grade Math » Unit: Congruence and Similarity
8th Grade Math » Unit: Congruence and Similarity
Mauricio Beltre
Orlando, FL
Environment: Urban
 
Big Idea:

Students recognize and use properties of lines and angle to determine angle measures.

 
Favorites (12)
 
Resources (14)
image day 2 angles parallel lines
   

Prove interior angles of a triangle using transversals

8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
Jeff Li MTP
New York, NY
Environment: Urban
 
Big Idea:

Get kids to prove facts using transversals. This is harder than it sounds!

 
Favorites (8)
 
Resources (17)
lesson 7 5 image 001
   

Special angle pairs

8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
Jeff Li MTP
New York, NY
Environment: Urban
 
Big Idea:

Set the foundation for logical reasoning by providing basic proofs of theorems about complementary, supplementary, and vertical angles.

 
Favorites (19)
 
Resources (16)
7 1 image special angle pairs resized
   

The Triangle Sum Setup

8th Grade Math » Unit: Congruence and Similarity
8th Grade Math » Unit: Congruence and Similarity
Mauricio Beltre
Orlando, FL
Environment: Urban
 
Big Idea:

Before using and applying the Triangle Sum Property, students verify it through a hands -on activity and by providing a proof.

 
Favorites (15)
 
Resources (17)
sum triangle angles image
   

Transversals 1

8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
Jeff Li MTP
New York, NY
Environment: Urban
 
Big Idea:

Parallel lines cut by a transversal are AMAZING! See what happens.

 
Favorites (17)
 
Resources (15)
7 2 image transversals 1
   

Angles and Parallel Lines (Day 1 of 2)

8th Grade Math » Unit: Congruence and Similarity
8th Grade Math » Unit: Congruence and Similarity
Mauricio Beltre
Orlando, FL
Environment: Urban
 
Big Idea:

Students recognize and use properties of lines and angle to determine angle measures.

 
Favorites (17)
 
Resources (19)
 
Reflections (1)
parallel parking
   

Defining Key Angle Relationships

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
Shaun Errichiello
New York, NY
Environment: Urban
 
Big Idea:

We should let students observe the relationships between different types of angles and develop their intuition.

 
Favorites (11)
 
Resources (14)
 
Reflections (1)
screen shot 2014 02 09 at 1 08 22 pm
   

Why Do Triangles Have 180 Degrees?

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
Shaun Errichiello
New York, NY
Environment: Urban
 
Big Idea:

Students realize that triangles are the basis for defining all angle measure.

Standards:
 
Favorites (2)
 
Resources (13)
 
Reflections (1)
hatlw
   

Why Are Vertical Angles Equal?

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
Shaun Errichiello
New York, NY
Environment: Urban
 
Big Idea:

Give students a chance to prove that all vertical angles are equal.

 
Favorites (4)
 
Resources (10)
verticalangles image
   

Angles and Algebra

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
Shaun Errichiello
New York, NY
Environment: Urban
 
Big Idea:

Using algebraic expressions for angles reinforces student understanding of basic algebra tools.

 
Favorites (7)
 
Resources (10)
angles and algebra image resized
   

Arrange 3 copies to prove interior angles of triangles

8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
Jeff Li MTP
New York, NY
Environment: Urban
 
Big Idea:

Get performance data on student mastery of this unit by assessing students on key concepts and practices.

 
Favorites (3)
 
Resources (19)
 
Reflections (1)
lesson 7 9 image
   

Discovering What it Means to be Similar Triangles

8th Grade Math » Unit: Linear Equations in two Variables
8th Grade Math » Unit: Linear Equations in two Variables
Christa  Lemily
Bowling Green, KY
Environment: Suburban
 
Big Idea:

Imagine teaching similarity, angle-angle similarity for triangles, and dilations all at once! It’s a three for one deal!

 
Favorites (12)
 
Resources (16)
 
Reflections (1)
discovering what it means to be similar tangrams
Common Core Math
 
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