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Lesson plan

7. Understand angles are composed of 1º angles (C)

teaches Common Core State Standards MP3 http://corestandards.org/Math/Practice/MP3
teaches Common Core State Standards 4.G.A.1 http://corestandards.org/Math/Content/4/G/A/1
teaches Common Core State Standards 4.MD.C.5.b http://corestandards.org/Math/Content/4/MD/C/5/b

7. Understand angles are composed of 1º angles (C)

Lesson objective: Understand that angles are composed of 1º angles.

Students bring prior knowledge of unit fractions from 3.NF.1. This prior knowledge is extended to angle measurement as students learn that 1º is equivalent to 1/360 of a circle and that angles are composed of 1º angles.  A conceptual challenge students may encounter is understanding that angular measurement is measuring rotation. 

The concept is developed through work with a circle, which has rays that intersect at a center point allowing students to visualize rotation and consider angle size based on reference lines. 

This work helps students deepen their understanding of operations because each angle is composed of 1º angles. The 1º angles can be combined by considering either addition or multiplication. 

Students engage in Mathematical Practice 3 (construct viable arguments and critique the reasoning of others) as they consider different points of view and develop strategies to solve and justify their reasoning with others. 

Key vocabulary:

  • angle
  • benchmark
  • compare
  • degree
  • right angle
  • rotate