Student Actions

Teacher Actions

• Develop a deep and flexible conceptual understanding of the types of angles, and comparison of angles (larger or smaller than 90 degrees).

• Develop mathematical reasoning when measuring angles with a protractor by recognizing the appropriate scale based on whether the angle is larger or smaller than 90 degrees (e.g., whether it is appropriate to use the inner scale or the outer scale on the protractor). 

• Build procedural fluency from conceptual understanding by modeling the proper use of the protractor and/or angle ruler, and providing multiple opportunities for students to measure angles in geometric figures and real-world contexts.

• Elicit evidence of student thinking in regard to the reasonableness of their measurement results, and use this evidence to assess progress toward mathematical understanding. 

Key Understandings

Misconceptions

• Angles can be identified as obtuse, acute, right, or straight angles.

• A protractor or angle ruler can be used to accurately measure angles (within 3 - 5 degrees) in geometric figures and real-world contexts.

• It is not important to align the protractor baseline with one of the rays of the angle.
• The length of the ray has an effect on the angle degree.
• Rays do not need to be extended in order to measure the angle accurately.