Lesson 1

Investigating Angles

Est. Class Sessions: 2
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Mathematical Standards

4.MD.C
Geometric measurement: understand concepts of angle and measure angles. (4.MD.C.5, 4.MD.C.6, 4.MD.C.7)

Standards for Mathematical Practice

MP1.
Make sense of problems and persevere in solving them.
MP2.
Reason abstractly and quantitatively.
MP3.
Construct viable arguments and critique the reasoning of others.
MP5.
Use appropriate tools strategically.

Students investigate angles in several contexts, including angles that occur inside of shapes, in everyday objects, and in geometric representations. Students compare and order angles by size, eventually classifying them into categories of right, acute, and obtuse.

Content in this Lesson

  • Classifying acute, obtuse, and right angles [E2].
  • Comparing and ordering angles by angle size [E11].
  • Estimating the size of an angle [E11].
  • Drawing angles [E12].
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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
scissors
ruler
straws (inflexible, 10 per student)
paper clips or pieces of chenille stems (5 per student)

Materials for the Teacher

chart paper
scissors
ruler
straws (inflexible, 6)
paper clips (2) or pieces of chenille stems (2)
Unit 9 Assessment Record
Math Facts Class Record

Materials Preparation

Cut Out Angle Cards. Cut out (or have student volunteers cut out) the Angle Sort Cards in the Student Activity Book and place them in envelopes in advance. Students will use these cards again in Lesson 4.

Make an Angle. Assemble an angle from two drinking straws and a paper clip or a piece of a chenille stem. Drinking straws should not be flexible. See Figure 1 in Part 2 of the lesson for tips on assembling the angles.

Geometry Word Chart. Prepare an area in your room for a Geometry Word Chart. The chart will be used to record students' vocabulary definitions. In Lesson 1, you will likely need two or three sheets of chart paper. On the first sheet, write the title “Geometry Word Chart” in large letters. Expect the size of the chart, and the area needed to display it, to grow as the unit progresses. It should be in a location that is easy for you and your students to write on, point to, and see from anywhere in the room. See Before the Lesson and Figure 6 for more information.

Assessment in this Lesson

Assessment Expectation Assessed

Investigating Angles
Check-In: Question 6
Student Guide Page 370

E2.
Classify acute, obtuse, and right angles.

DPP Item A
Triangle Flash Cards: Square Numbers
Teacher Guide - digital

E13.
Demonstrate fluency with the division facts for the square numbers.