1. Radians, Degrees, Arc Length, & Area of a Sector
AS Maths with Liz
Core 2

2. By the end of this lesson you will be able to…
Convert between radians and degrees
Work out the length of an arc
Calculate the area of a given sector
Find the area of a segment

3. So far in maths… you have measured angles in degrees
However, angles can also be measured in radians. The symbol for this is

4. It’s almost an “equilateral arc”
What is a radian?
A radian is an angle measured based on the radius of a circle. One radian is defined by the angle at the centre of an arc where the arc length is the same as the radius.
It’s almost an “equilateral arc”

5. Calculating 1c in degrees
To calculate one radian, recall the arc length formula:
Key Facts:

6. Example 1 – Converting between Degrees & Radians
Convert the following (a) in radians (b) in degrees (c) in degrees (d) in radians

7. You try:
Convert the following (a) in radians (b) in degrees (c) in degrees (d) in radians

8. Arc Length

9. Sector Area

10. Example 2

11. You try

13. Independent Study Core 2 textbook
Pg. 389, Exercise 9A, #1 – 4 only
DUE TUESDAY, JAN. 13TH
Core 1 Past Paper – January 2012 (blue booklet)
Please complete all questions on A4 paper
Mark your work in colourful pen answers on moodle
No gaps! (come to drop in for help)
Correct any necessary
DUE FRIDAY, JAN. 9TH