Page 121 - IM_FL_Geometry_Print Sample

Lesson 5: Angles, Sectors, and Arcs
• Practice calculating arc length and sector area.
Lesson Narrative
This lesson is optional because it is an opportunity for extra practice that not all classes may need.
This lesson invites students to use what they have learned about angle, radius, arc length, and sector area to solve problems and build procedural uency.
Students reason abstractly and quantitatively when they, for example, solve for the radius necessary to make two sectors with di erent central angles have the same area (MP2).
Required Materials Scienti c calculators
Student Learning Goals
• Let’s practice nding arc length and sector area. 5.1 Math talk: Estimating Angles
Warm Up: 5 minutes
The purpose of this Math Talk is to build uency with radian measure by encouraging students to think about relative sizes of di erent radian measures.
Instructional Routines
• Math talk
What: In these warm-ups, one problem is displayed at a time. Students are given a few minutes to quietly think and give a signal when they have an answer and a strategy. The teacher selects students to share di erent strategies for each problem, “Who thought about it a di erent way?” Their explanations are recorded for all to see. Students might be pressed to provide more details about why they decided to approach a problem a certain way. It may not be possible to share every possible strategy for the given limited time; the teacher may only gather two or three distinctive strategies per problem. Problems are purposefully chosen to elicit di erent approaches, often in a way that builds from one problem to the next.
Why: Math talks build uency by encouraging students to think about the numbers, shapes, or algebraic expressions and rely on what they know about structure, patterns, and properties of operations to mentally solve a problem. While participating in these activities, students need to be precise in their word choice and use of language (MP6).
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Teacher Guide