Lesson 5

Angles in Polygons

Est. Class Sessions: 3
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Mathematical Standards

4.MD.C
Geometric measurement: understand concepts of angle and measure angles. (4.MD.C.6, 4.MD.C.7)
4.G.A
Draw and identify lines and angles, and classify shapes by properties of their lines and angles. (4.G.A.2)

Standards for Mathematical Practice

MP1.
Make sense of problems and persevere in solving them.
MP2.
Reason abstractly and quantitatively.
MP5.
Use appropriate tools strategically.
MP6.
Attend to precision.

Students build upon their angle measurement and estimation skills by measuring the angles inside polygons and exploring the relationship between the angles in a triangle. They also begin to classify shapes, starting with the classification of triangles based on their angle measures.

Content in this Lesson

  • Identifying shapes that are polygons [E5, E6].
  • Measuring angles in a polygon [E12].
  • Finding the sum of the angles in a triangle [E1].
  • Finding a missing angle measure in a triangle [E1].
  • Classifying acute, obtuse, and right triangles [E2].
  • Using addition and subtraction to find unknown angles [E1].
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Materials for Students

Daily Practice and Problems Lesson Homework Assessment

Student Books

 Student Guide
Student Activity Book

Teacher Resources

 Teacher Guide - digital

Supplies for Students

envelope with the following Power Polygons™:
1 yellow square (A)
1 orange square (B)
1 blue rectangle (C)
1 red triangle (D)
1 large green triangle (E)
1 brown triangle (F)
1 green rhombus (G)
1 yellow hexagon (H)
1 blue triangle (I)
1 yellow triangle (J)
1 red trapezoid (K)
1 orange triangle (L)
1 blue rhombus (M)
1 small green triangle (N)
1 brown rhombus (O)
protractor
ruler

Materials for the Teacher

chart paper. See Materials Preparation.
protractor (optional)
Display of Geometry Word Chart (from Lessons 1–4)
Display of What Is a Polygon? Master (Teacher Guide)
Display of Add and Subtract Angles Question 5 (Student Activity Book) Page 333
Display set of Power Polygons™. See Supplies for Students.
Unit 9 Assessment Record

Materials Preparation

Geometry Word Chart. Prepare and post two sheets of chart paper to add to the Geometry Word Chart. The term polygon will be added to the chart in Part 1 of the lesson. Write this word in large letters on the chart with plenty of blank space surrounding it.

Power Polygons™. Place one set of the Power Polygons™ listed in the Supplies for Students section into an envelope for each student.

Assessment in this Lesson

Assessment Expectation Assessed Math Practices Expectation Assessed

Lines, Angles, and Polygons Quiz with Feedback Box
Teacher Guide - digital
E1.
Use addition and subtraction to find unknown angles.
E2.
Classify acute, obtuse, and right angles.
E3.
Identify points, rays, lines, and line segments.
E4.
Draw and identify intersecting, perpendicular, and parallel lines.
E11.
Estimate the size of an angle using 90°, 180°, and 360° as benchmarks.
E12.
Use a protractor to measure and draw angles to the nearest degree.
MPE3.
Check for reasonableness. I look back at my solution to see if my answer makes sense. If it does not, I try again.
MPE6.
Use labels. I use labels to show what numbers mean.