Radian Measure

Central Angle: angle formed at the center of the circle by the two radii.

 

Sector: Area formed by the radii and arc of the circle

 

Radian: Measure of an angle in radians = Arc Length / Radius

 

Angular Velocity: The Rate of Change of the central angle measured in radians/second

 

 

Ang. Velocity = (Total Degrees or Radians Travelled) / (Time)

Ang. Velocity = Change in Angle/Time

 

In Degrees measure, 1 complete rotation is 360 degrees.

In Radian measure, 1 complete rotation is 2pi.

 

360 = 2pi Rad

360/360 = 2pi rad /360

1 = pi / 180 rad

 

2pi rad = 360

1 rad = 360 / 2pi

1 rad = 180 / pi

 

Therefore to convert to Radians or Degrees just multiply by (180/pi) or (pi/180).

 

 

Important Formula: Angle = Arc / Radius

 

 

Example

 

Angle = ?

Arc = 3 cm

Radius = 9cm

 

Solution : Angle is 1/3 rad.

 

 

If you have any questions, leave them in the comments below.