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.

[u][size=150][b][size=200]Activity Instructions[/size][/b][/size][br][br][/u][size=150][u](Use the checkboxes to unhide/hide items mentioned)[br][br][/u]1. Use the protractor (unhide using protractor checkbox) to measure the angle.[br]2. Extend the rays of the angle.[br]3. Show circle1 and arc1. [br] Arc1 in circle 1 subtends the angle at the centre of circle[br]4. Show circle and arc2[br] Arc2 in circle 2 subtends the [b][u]same angle [/u][/b]at the common [u][b]centre of circle[/b][/u].[br]5. Show radian calculations. Explain how the radian concept is applied to any angles.[br] The angle is measured as a ratio of the arc length divided by the radius of the arc.[br] It is not how large or small you make the arc.[br] For any angle, the arc length (circular) divided by the radius is a constant .[br]6. Drag H to change the sizes of circle2. Notice no change in angle in degree or radian.[br]7. Drag Q or click on "Random" button to change angle[/size][br] [br]