Try describing the angle of the shaded areas without using degrees

Radians

• What is a Radian?• How to convert degrees into Radians• How to convert Radians into degrees• How to calculate the length of an Arc• How to calculate the area of a sector

r

r

Radians

r

r

r

A Radian is a unit used to measure angles.

One Radian is the angle that cuts out a length of the circumference that’s equal to the radius1 rad

RadiansQuick facts to remember!

There is π rads (or 3.14 rads) in half a circle, and 2π rads in one full circle.

How many degrees is there in 1 radian then?

180radians

180radians 1 ...2958.57radians 1

Radians or Degrees?Changing from Radians or Degrees use these

rules

Degrees180

Radians

From Radians to Degrees

Radians180

Degrees From Degrees

to Radians

Degrees to Radians Example

18030

What is 30˚ in Radians?

rad6

What is 90˚ in Radians?

18090

rad

2

Radians to Degrees Examples

180

3

What is π/3 rad in Degrees?

60

What is 3π/2 rad in Degrees?

180

2

3 270

Question Time

Have a go at Q1, 2, and 3 on

the back

Length of an Arc

s rs s = length of arcr = radiusӨ = angle in rad

Area of a Sector

22

1rA

A = Area of sectorr = radiusӨ = angle in rad

A

Question Time

rs

22

1rA

Try out Q5, 6 and exam question

Independent Study

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