Section+1-2

1.2-Radian Measure, Arc Length, and Area

Radian Measures of Angles- For radian measure of angles in standard position we use a unit circle(a circle with radius 1)centered at the origin.

Definition:Radian Measure The radian measure of the angle a in standard position is the directed length of the intercepted arc on the unit circle.

Degree-Radian Conversion-Conversion from degrees to radians or radians to degrees is based on 180 degrees = pie radians.

To convert degrees to radians or radians to degrees, use 180 degrees=pie radians and cancellation of units. For example

Theorem: Length of an Arc-- The length s of an arc intercepted by a central angle of a radians on a circle of radius r is given by-- s-ar. Area of a sector of a circle: A sector of a circle is the region between two radii of a circle.
 * Note: The formula given above only applies if a is in radians.**