# Measurement of Angles (From degree to radian)

- Author:
- Lew W.S.

This resource can be used in class to help students to move from measuring angles in degrees (protractor supplied) to thinking and understanding of the use of the radian measure.

**Activity Instructions**__(Use the checkboxes to unhide/hide items mentioned)__1. Use the protractor (unhide using protractor checkbox) to measure the angle. 2. Extend the rays of the angle. 3. Show circle1 and arc1. Arc1 in circle 1 subtends the angle at the centre of circle 4. Show circle and arc2 Arc2 in circle 2 subtends the

**at the common**

__same angle____. 5. Show radian calculations. Explain how the radian concept is applied to any angles. The angle is measured as a ratio of the arc length divided by the radius of the arc. It is not how large or small you make the arc. For any angle, the arc length (circular) divided by the radius is a constant . 6. Drag H to change the sizes of circle2. Notice no change in angle in degree or radian. 7. Drag Q or click on "Random" button to change angle__

**centre of circle**An angle measured in radians is

1 radian =

1 degree =

Which of the following is true