Find the length of the arc of a circle of diameter 42 cm which subtends an angle of 60° at the centre.

Given:

Diameter of circle = 42 cm

⇒ Radius of circle = cm = 21 cm

Angle subtended at the centre = 60°

∵ Length of arc = × 2πr

=

= 22 cm

Hence, the length of the arc is 22 cm.