Education Technology

Geometry: Arc Length and Sectors
by Texas Instruments

Updated on August 18, 2014

Objectives

  • Students will recognize that the sum of two central angles that combine to make a circle is 360°.
  • Students will recognize that the ratio of the central angle to 360° determines the length of an arc.
  • Students will recognize that the ratio of the central angle to 360° determines the area of a sector.

Vocabulary

  • circumference
  • area
  • arc
  • sector angle (or central angle)
  • arc measure
  • arc length
  • sector

About the Lesson

This lesson involves dragging a point around a circle to see how arcs and sectors change as the central angle defining them changes. As a result, students will:

  • Watch the central angles, sectors, and accompanying ratios change as they drag a point around a circle.
  • Specify the percentages (ratios) of circumference and area for various central angles.
  • Identify the connection between the central angle and the percentage of circumference and area used to determine arc length and sector area.