Radian Measure, Arcs, Sectors, Area

Key Ideas

• Why do we use radians if we already have degrees?

• Equivalent measurement systems, such as degrees and radians, can be used for angles to facilitate ease of calculation.

• Different representations of the values of trigonometric relationships, such as exact or approximate, may not be equivalent to one another.

• The trigonometric functions of angles may be defined on the unit circle, which can visually and algebraically represent the periodic or symmetric nature of their values.

Arc length and the Area of a sector

Finding the length of an arc and the area of a sector is easier when working in radians. Make sure you know the difference between a minor an major arc and watch the video above, prior to the lesson

Activity: Arc equals Radius

With your group, on a A3 piece of paper:  Find the angle at which the arc equals the radius. Show a graphic, a calculation and your answer. 

TiP: Use your knowledge about the circumference of a circle.