Curriculum  /  Math  /  4th Grade  /  Unit 8: Shapes and Angles  /  Lesson 2

Shapes and Angles

Lesson 2

Math

Unit 8

4th Grade

Lesson 2 of 18

Objective

Identify and draw right, obtuse, and acute angles.

Common Core Standards

Core Standards

  • 4.G.A.1 — Draw points, lines, line segments, rays, angles (right, acute, obtuse), and perpendicular and parallel lines. Identify these in two-dimensional figures.

Foundational Standards

  • 3.G.A.1

Criteria for Success

  1. Understand that a right angle is a square corner.
  2. Understand that an acute angle is one that measures less than a right angle.
  3. Understand that an obtuse angle is one that measures greater than a right angle but less than a straight angle. 
  4. Understand that a straight angle is one that is formed by three points that are all on the same line.
  5. Determine whether angles are right, obtuse, or acute using a right-angle tool (MP.5).
  6. Draw right, obtuse, and acute angles (MP.5, MP.6).

Tips for Teachers

  • Note that students will later see that a right angle is the angle formed by perpendicular lines and measures 90°, more precise definitions of right angles. However, because these terms and concepts have not yet been introduced, the definition is somewhat informal for the time being.
  • Students are going to create a right-angle tool in this lesson. Have students save this tool for future lessons.

Lesson Materials

  • Blank Paper (1 sheet per student) — Ideally the paper is circular, though this isn't necessary
  • Template: Angles (1 per student or small group) — See Anchor Task 1 for how to prepare this material before the lesson.
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Anchor Tasks

25-30 minutes

Problem 1

Sort the angles (cut out from Template: Angles) into as many groups as you like. Be prepared to explain how you sorted your angles. 

Guiding Questions

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Student Response

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References

EngageNY Mathematics Grade 4 Mathematics > Module 4 > Topic A > Lesson 2 — Concept Development Problem 2

Grade 4 Mathematics > Module 4 > Topic A > Lesson 2 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..

Modified by Fishtank Learning, Inc.

Problem 2

Draw an example of a right angle, an acute angle, an obtuse angle, and a straight angle.

Guiding Questions

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Student Response

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References

EngageNY Mathematics Grade 4 Mathematics > Module 4 > Topic A > Lesson 2 — Concept Development Problem 3

Grade 4 Mathematics > Module 4 > Topic A > Lesson 2 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..

Problem Set

15-20 minutes

Discussion of Problem Set

  • #1(c) and 1(f) are both right angles. Describe their position. Does the orientation of an angle determine whether it is right, acute, or obtuse?
  • In #3(a), each ray shared the same endpoint. The shared endpoint is called a vertex. Label the points on your angles in #3. Identify the vertex in #3(b) and 3(c) with your partner.
  • What is the difference between a straight angle and a line?
  • Where else in your environment have you seen right angles?
  • How did the right-angle tool help you recognize and draw angles? How can a right-angle tool help you recognize an acute angle?

Target Task

5-10 minutes

Problem 1

Use the following angles to answer the questions below. 

A. 

B. 

C. 

D. 

E. 

F. 

G. 

H. 

Write the letters of the angles that are:

right angles: _____________________

acute angles: _____________________

obtuse angles: _____________________ 

straight angles: _____________________

Student Response

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Problem 2

Draw an additional example of each type of angle below. 

a.   Right angle:

b.   Obtuse angle:

c.   Acute angle:

d.   Straight angle:

Student Response

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Additional Practice

The Extra Practice Problems can be used as additional practice for homework, during an intervention block, etc. Daily Word Problems and Fluency Activities are aligned to the content of the unit but not necessarily to the lesson objective, therefore feel free to use them anytime during your school day.

Word Problems and Fluency Activities

Word Problems and Fluency Activities

Help students strengthen their application and fluency skills with daily word problem practice and content-aligned fluency activities.

Next

Identify and draw perpendicular lines.

Lesson 3
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Lines and Angles

Topic B: Measures of Angles

Topic C: Measures of Adjacent Angles

Topic D: Shapes and Lines of Symmetry

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