Geogebra - Find a rule for the sector area of a circle angle α

In this activity will use the area formula π r2 to make a formula for any kind of circle sector!

  1. Load this Geogebra file.

You should see this sector.
  1. Now move point Sector rotator to position (4,4)

You should see the acute angle get smaller.

  1. Use the spreasheet to confirm the area of the circle.  You type = π * 5 * 5
  2. The answer should be 79 !
  

 
Questions
  1. What was the value of  the Free Object C when the Sector rotator was at angle 45º?
  2. What was the value of  the Conic C ( Free Object C ) when the Sector rotator was at angle 180º?
  3. Make a formula on the spreadsheet that would calculate the area of a sector with angle 180º
  4. What is the formula for a area of a generalised sector with angle α ?
Activities
  1. Change the object properties of point B.  You must untick the "Fix Object" box to be able to move point B
  2. Save a copy of your new sector in your "Maths is Amazing" folder.