Find Radian Measure by Dividing Arc Length by Radius

This Find Radian Measure by Dividing Arc Length by Radius video also includes:

In an approach that meshes higher-level thinking with approachable methods, this presentation walks that fine line between mathematical rigor and applications with skill. Not only are the specific steps for finding the radian measure of central angles demonstrated, but the relationships inside each circle that allow for using these steps are explained. Common pitfalls are detailed out, specifically the difference between the constant pi and the variable theta, and several key examples shown and worked explicitly. A great introduction or quick refresher video for group or solo viewing. 

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CCSS: Designed
Instructional Ideas

  • Assign this video for before-class viewing to mesh nicely with the flipped classroom model
  • Extend the introduction by having learners bring circular objects from home and measure radius vs. circumference to discover the common ratio of pi themselves
  • Use sectors of circular food as delicious manipulative examples. Cheese wedges, bakery pies, or cake slices would all work for activities
Classroom Considerations

  • Adobe Flash and Internet access required for video viewing, so possible updates and streaming access needed
  • Creation of a free LearnZillion account required to use this lesson
  • Slides of the video presentation available under the Additional Materials tab on the LearnZillion website
  • Material presented assumes the class is familiar with the labeling of angles with the greek letter theta

  • The formula is derived from basic principles
  • Pleasant and easy-to-understand narrator
  • Pacing is quick enough to maintain interest, but slow enough to allow ideas to fully develop

  • No independent practice problems provided
  • No negative or fractional angle measures covered
Common Core