Math 20-2

Chapter 2 Properties of Angles and Triangles

Lesson 2.4 Angle Properties in Polygons

GOAL

The goal of this lesson is stated at the top of page 94 in your textbook, and is also written below.
Keep this in mind as you work through the lesson material.

Determine properties of angles in polygons, and use these properties to solve problems.

Explore...

Try to answer the question in the sidebar on page 94.

Watch

Video Tutorial

Investigate the Math

Investigate an idea or problem, with a partner if possible.
The investigation provides the background for the ideas presented in the lesson.

TEXT Pages 94 - 95

Read/Work through the Investigate section on Pages 94-95 in your textbook.

Go through this material,  AS BEST YOU CAN,  before you view the video tutorials that follow.

Introduction

Video Tutorial  (review of interior and exterior angles of a triangle)

You can experiment with this interactive triangle as a reminder of some of the ideas we have explored connected to angles in a triangle.
... and this interactive triangle shows the other important idea from the previous lesson

?  How is the number of sides in a polygon related to the sum of its interior angles and the sum of its exterior angles?

Be sure to work through the investigation as best as you can, before you watch the video!!

Video Tutorial

Parts D and E  Video Tutorial  (Interior angle conjecture)

Exterior Angles   Parts F -J  Video Tutorial

Apply the Math  (Examples)

Examples will give you TOOLS for solving problems, and also show you that there may be different ways to approach a question.

YOUR TURN gives YOU the chance to try to do a problem ON YOUR OWN,  using the examples as models.

Example 1  Reasoning about the sum of the interior angles of a polygon

TEXT Page 96

Work through Example 1 on Page 96 in your textbook.

Watch

Video Tutorial

Your Turn

Use the Video Tutorial for help, or to check your work, BUT... you should do your best to do this question ON YOUR OWN FIRST!

Video Tutorial

Example 2  Reasoning about angles in a regular polygon

TEXT Page 97

Work through Example 2 on Page 97  in your textbook.

Watch

Video Tutorial

Your Turn

Use the Video Tutorial for help, or to check your work, BUT... you should do your best to do this question ON YOUR OWN FIRST!

Video Tutorial

Example 3  Visualizing tessellations

TEXT Page 98

Work through Example 3 on Page 98 in your textbook.

Watch

Video Tutorial

Your Turn

Use the Video Tutorial for help, or to check your work, BUT... you should do your best to do this question ON YOUR OWN FIRST!

Video Tutorial

In Summary

Key Ideas and Need to Know 
Presents and summarizes  the main new concepts of the lesson

•	Carefully read through each of the bullet points in this section.

•	If you are unclear about any of these ideas,  ASK YOUR TEACHER FOR HELP!

Practice Problems

Doing Practice Problems

Practice problems reinforce the math presented in this lesson.

•	Work through the practice problems for this lesson.
	These problems are for practice, you don’t need to hand them in!
	(your teacher may assign specific questions for you to complete)

•	Use the answers in the back of the book to CHECK YOUR WORK!

•	If you make a mistake, TRY TO FIX IT!

•	If you need help or want more information, view the video solutions provided.

•	If you still need more help,  CONTACT YOUR TEACHER!

Types of Practice Problems

Check Your Understanding questions require basic understanding of the ideas of the  lesson.

Practising questions will require you to dig deeper for a solution.

Closing  A summary question that often asks YOU to explain ideas in your own words.

Extending questions offer enrichment and extension.

Notes

Question 19,    I didn’t do a video for this one.

Video Solution Links

Check your work for every problem you do!
If you make a mistake,  try to fix it!
Use the video solutions for more information.
If a problem still doesn’t make sense, ASK YOUR TEACHER FOR HELP!

({{"Question 1", "Question 2", "Question 3", "Question 4", "Question 5"}, {"Question 6", "Question 7", "Question 8", "Question 9", "Question 10"}, {"Question 11", "Question 12", "Question 13", "Question 14", "Question 15"}, {"Question 16", "Question 17", "Question 18",  , "Question 20"}, {"Question 21", , , , }})