An arc (Circular Arc) is defined as a piece of the circumference.
Depending on the size of the arc, we can divide arcs into either a major arc (> 0.5 of the circumference) or a minor arc (< 0.5 of the circumference).
Formula
The circumference of a circle = 2πr
The length of an arc is a fraction (θ out of 360°) of the circumference where θ is the angle subtended to the centre. This angle is sometimes referred to as the central angle.
Arc Length
We use the letter 's' to represent the length of an arc. There are 2 formulas for finding the length of an arc.
Check out the applet below to see the 2 formulas in action.
Move the slider bar to change the angle that sweeps out the arc as well as the radius.
Check on the box to switch from degree mode to radian mode formula.
Test Yourself!
Check your understanding using the randomised auto-marking quiz below. How many points can you score in 10 minutes?
Use the red slider bar to toggle the question types: Degree Questions only, Radian Questions only or a mix of the two.